AIX 5.3 STIG
AIX 5.3 SECURITY TECHNICAL IMPLEMENTATION GUIDE. Version v1 r3, released Oct. 24, 2014.
GEN004950: The ftpusers file must not have an extended ACL.
Check the permissions of the /etc/ftpusers file. #aclget /etc/ftpusers Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Excessive permissions on the ftpusers file could permit unauthorized modification. Unauthorized modification could result in Denial of Service to authorized FTP users or permit unauthorized users to access the FTP service.
Fix
Remove the extended ACL from the ftpusers file and disable extended permissions. #acledit /etc/ftpusers
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003420: The at directory must be owned by root, bin, sys, daemon, or cron.
Check the ownership of the at directory. Procedure: # ls -ld /var/spool/cron/atjobs If the directory is not owned by root, bin, sys, daemon, or cron, this is a finding.
Discussion
If the owner of the at directory is not root, bin, sys, daemon, or cron unauthorized users could be allowed to view or edit files containing sensitive information within the directory.
Fix
Change the owner of the at directory to root, bin, sys, daemon, or cron. Procedure: # chown bin /var/spool/cron/atjobs
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001720: All global initialization files must have mode 0644 or less permissive.
Check global initialization files permissions: # ls -l /etc/.login /etc/profile /etc/bashrc /etc/environment /etc/security/environ /etc/security/.profile /etc/csh.login /etc/csh.cshrc If global initialization files are more permissive than 0644, this is a finding.
Discussion
Global initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.
Fix
Change the mode of the global initialization file(s) to 0444. # chmod 0444 <global initialization file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002751: The audit system must be configured to audit account modification.
Determine if the audit system is configured to audit account modification. Procedure: # more /etc/security/audit/events If auditing of the USER_Change event is not configured, this is a finding. Verify the USER_Change audit event is defined in the audit classes' stanza classes: of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config Make note of the audit class(es) the USER_Change event is associated with. If the USER_Change event is not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config If the class(es) the USER_Change event is not associated with the default user and all the system users in the users: stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Configure the system to audit account modification. Edit /etc/security/audit/events and add the USER_Change event to the list of audited events. Edit /etc/security/audit/config and add the USER_Change audit event to an audit class in the classes: stanza. Edit /etc/security/audit/config and assign the audit classes with the USER_Change event to the all users listed in the users: stanza.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001364: The /etc/resolv.conf file must have mode 0644 or less permissive.
Check the mode of the /etc/resolv.conf file. Procedure: # ls -l /etc/resolv.conf If the file mode is more permissive than 0644, this is a finding.
Discussion
The resolv.conf (or equivalent) file configures the system's DNS resolver. DNS is used to resolve host names to IP addresses. If DNS configuration is modified maliciously, host name resolution may fail or return incorrect information. DNS may be used by a variety of system security functions, such as time synchronization, centralized authentication, and remote system logging.
Fix
Change the mode of the /etc/resolv.conf file to 0644 or less permissive. # chmod 0644 /etc/resolv.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001220: All system files, programs, and directories must be owned by a system account.
Check the ownership of system files, programs, and directories. Procedure: # ls -lLa /etc /bin /usr/bin /usr/lbin /usr/ucb /sbin /usr/sbin If any of the system files, programs, or directories are not owned by a system account, this is a finding. For this check, the system-provided "ipsec" user is considered to be a system account.
Discussion
Restricting permissions will protect the files from unauthorized modification.
Fix
Change the owner of system files, programs, and directories to a system account. Procedure: # chown root /some/system/file (A different system user may be used in place of root.)
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003200: The cron.deny file must have mode 0640 or less permissive.
Check the mode of the cron.deny file. # ls -lL /var/adm/cron/cron.deny If the cron.deny file is more permissive than 0640, this is a finding.
Discussion
If file permissions for cron.deny are more permissive than 0640, sensitive information could be viewed or edited by unauthorized users.
Fix
Change the mode of the cron.deny file. # chmod 0640 /var/adm/cron/cron.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005260: X Window System connections not required must be disabled.
Determine if the X Window system is running. Procedure: # ps -ef |grep X Ask the SA if the X Window system is an operational requirement. If it is not, this is a finding.
Discussion
If unauthorized clients are permitted access to the X server, the user's X session may be compromised.
Fix
Disable the X Windows server on the system. Comment out /etc/rc.dt out of /etc/inittab
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004010: The traceroute file must not have an extended ACL.
Check the permissions of the /usr/sbin/traceroute file. #aclget /usr/sbin/traceroute Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
If an extended ACL exists on the traceroute executable file, it may provide unauthorized users with access to the file. Malicious code could be inserted by an attacker and triggered whenever the traceroute command is executed by authorized users. Additionally, if an unauthorized user is granted executable permissions to the traceroute command, it could be used to gain information about the network topology behind the firewall. This information may allow an attacker to determine trusted routers and other network information possibly leading to system and network compromise.
Fix
Remove the extended ACL from the traceroute file and disable extended permissions. #acledit /usr/sbin/traceroute
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007880: The system must not send IPv6 ICMP redirects.
# /usr/sbin/no -o ipsendredirects If the value returned is not 0, this is a finding.
Discussion
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table that could reveal portions of the network topology.
Fix
Configure the system to not send IPv6 ICMP redirects. # /usr/sbin/no -p -o ipsendredirects=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001270: System log files must not have extended ACLs, except as needed to support authorized software.
Determine if any system log file has an extended ACL. If an extended ACL exists, verify with the SA if the ACL is required to support authorized software and provides the minimum necessary permissions. If an extended ACL exists that provides access beyond the needs of authorized software, this is a finding. Check to see if extended permissions are disabled. #aclget <directory>/<file>
Discussion
If the system log files are not protected, unauthorized users could change the logged data, eliminating its forensic value. Authorized software may be given log file access through the use of extended ACLs when needed and configured to provide the least privileges required.
Fix
Remove the extended ACL(s) from the system log file(s) and disable extended permissions. # acledit < directory >/< file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001367: The /etc/hosts file must be group-owned by bin, sys, or system.
Check the /etc/hosts file's group ownership. Procedure: # ls -lL /etc/hosts If the file is not group-owned by bin, sys, or system, this is a finding.
Discussion
The /etc/hosts file (or equivalent) configures local host name to IP address mappings that typically take precedence over DNS resolution. If this file is maliciously modified, it could cause the failure or compromise of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.
Fix
Change the group owner of the /etc/hosts file to sys, bin, or system. Procedure: # chgrp system /etc/hosts
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002710: All system audit files must not have extended ACLs.
Procedure: # grep -p bin: /etc/security/audit/config Directories and files to search will be listed under the bin stanza. #aclget <directory>/<file> Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
If a user can write to the audit logs, then audit trails can be modified or destroyed and system intrusion may not be detected.
Fix
Remove the extended ACL from the system audit file(s) and disable extended permissions. #acledit <directory>/<file> and disable extended permissions
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001260: System log files must have mode 0640 or less permissive.
Check the mode of log files. Procedure: # ls -lL /var/log /var/log/syslog /var/adm If any of the log files have modes more permissive than 0640, this is a finding.
Discussion
If the system log files are not protected, unauthorized users could change the logged data, eliminating its forensic value.
Fix
Change the mode of the system log file(s) to 0640 or less permissive. Procedure: # chmod 0640 /path/to/system-log-file NOTE: Do not confuse system log files with audit logs. Any subsystems that require less stringent permissions must be documented.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005501: The SSH client must be configured to only use the SSHv2 protocol.
Check the SSH client configuration for allowed protocol versions. # grep -i protocol /etc/ssh/ssh_config | grep -v '^#' If the variables Protocol 2,1 or Protocol 1 are defined on a line without a leading comment, this is a finding. If the SSH client is F-Secure, the variable name for SSH 1 compatibility is Ssh1Compatibility, not protocol. If the variable Ssh1Compatiblity is set to yes, this is a finding.
Discussion
SSHv1 is not a DoD-approved protocol and has many well-known vulnerability exploits. Exploits of the SSH client could provide access to the system with the privileges of the user running the client.
Fix
Edit the /etc/ssh/ssh_config file and add or edit a Protocol configuration line that does not allow versions less than 2.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007720: The IPv6 protocol handler must be prevented from dynamic loading unless needed.
Determine if the IPv6 protocol handler is prevented from dynamic loading. AIX comes with IPv6 protocol handler installed and active. The only IPv6 address configured by default is the loopback localhost adapter. #ifconfig -a If there is any unneeded IPv6 addresses on network interfaces, this is a finding.
Discussion
IPv6 is the next generation of the Internet protocol. Binding this protocol to the network stack increases the attack surface of the host. Unprivileged local processes may be able to cause the system to dynamically load a protocol handler by opening a socket using the protocol.
Fix
There is not an option to not load IPv6. Remove unnecessary IPv6 addresses from network interfaces via smit. #smit chinet6
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003603: The system must not respond to ICMPv4 echoes sent to a broadcast address.
# /usr/sbin/no -o bcastping If the value returned is not 0, this is a finding.
Discussion
Responding to broadcast Internet Control Message Protocol (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.
Fix
Configure the system to ignore ICMP ECHO_REQUESTs sent to broadcast addresses. # no -po bcastping=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004600: The SMTP service must be an up-to-date version.
Determine the version of the SMTP service software. Locate the sendmail daemon. Procedure: # find / -name sendmail Obtain version information for the Sendmail daemon. Procedure: # what < file location > OR # strings < file location > | grep version OR # echo \$Z | sendmail -d0 Version 8.14.5 is the latest released version. If the Sendmail version is not at least 8.14.5 or the vendor's latest version, this is a finding.
Discussion
The SMTP service version on the system must be current to avoid exposing vulnerabilities present in unpatched versions.
Fix
Obtain and install a newer version of Sendmail from the operating system vendor or from http://www.sendmail.org or ftp://ftp.cs.berkeley.edu/ucb/sendmail.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN005512: The SSH client must be configured to only use Message Authentication Codes (MACs) employing FIPS 140-2 approved cryptographic hash algorithms.
Check the SSH client configuration for allowed MACs. # grep -i macs /etc/ssh/ssh_config | grep -v '^#' If no lines are returned, or the returned MACs list contains any MAC other than hmac-sha1, this is a finding.
Discussion
DoD information systems are required to use FIPS 140-2 approved cryptographic hash functions.
Fix
Edit the SSH client configuration and remove any MACs other than hmac-sha1. If necessary, add a MACs line.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001560: All files and directories contained in user's home directories must have mode 0750 or less permissive.
For each user in the /etc/passwd file, check for files and directories with a mode more permissive than 0750. Procedure: # find /<usershomedirectory> ! -fstype nfs ! \( -name .login -o -name .cshrc -o -name .logout -o -name .profile -o -name .bash_profile -o -name .bashrc -o -name .env -o -name .dtprofile -o -name .dispatch -o -name .emacs -o -name .exrc \) \( -perm -0001 -o -perm -0002 -o -perm -0004 -o -perm -0020 -o -perm -2000 -o -perm -4000 \) -exec ls -ld {} \; If user's home directories contain files or directories more permissive than 0750, this is a finding.
Discussion
Excessive permissions allow unauthorized access to user's files.
Fix
Change the mode of files and directories within user's home directories to 0750. Procedure: # chmod 0750 filename Document all changes.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN002560: The system and user default umask must be 077.
Check global initialization files for the configured umask value. Procedure: # grep umask /etc/* Check local initialization files for the configured umask value. Procedure: # grep umask /userhomedirectory/.* If the system and user default umask is not 077, this is a finding. NOTE: If the default umask is 000 or allows for the creation of world-writable files, this becomes a Severity Code I (CAT I) finding.
Discussion
The umask controls the default access mode assigned to newly created files. An umask of 077 limits new files to mode 700 or less permissive. Although umask can be represented as a 4-digit number, the first digit representing special access modes is typically ignored or required to be 0. This requirement applies to the globally configured system defaults and the user defaults for each account on the system.
Fix
Edit local and global initialization files that contain "umask" and change them to use 077 instead of the current value.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003400: The at directory must have mode 0755 or less permissive.
Check the mode of the at directory. # ls -lLd /var/spool/cron/atjobs If the directory mode is more permissive than 0755, this is a finding.
Discussion
If the at directory has a mode more permissive than 0755, unauthorized users could be allowed to view or to edit files containing sensitive information within the at directory. Unauthorized modifications could result in Denial of Service to authorized at jobs.
Fix
Change the mode of the "at" directory to 0755. Procedure: # chmod 0755 < at directory >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006280: The /etc/news/hosts.nntp.nolimit (or equivalent) must have mode 0600 or less permissive.
Check /etc/news/hosts.nntp.nolimit permissions. # find / -name hosts.nntp.nolimit # ls -lL < hosts.nntp.nolimit file > If hosts.nntp.nolimit has a mode more permissive than 0600, this is a finding.
Discussion
Excessive permissions on the hosts.nntp.nolimit file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.
Fix
Change the mode of hosts.nntp.nolimit to 0600. # chmod 0600 < hosts.nntp.nolimit file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004920: The ftpusers file must be owned by root.
Check the ownership of the ftpusers file. # ls -l /etc/ftpusers If the ftpusers file is not owned by root, this is a finding.
Discussion
If the file ftpusers is not owned by root, an unauthorized user may modify the file to allow unauthorized accounts to use FTP.
Fix
Change the owner of the ftpusers file to root. # chown root /etc/ftpusers
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000320: All accounts must be assigned unique User Identification Numbers (UIDs).
Perform the following to ensure there are no duplicate UIDs: # usrck -n ALL If any duplicate UIDs are found, this is a finding.
Discussion
Accounts that share a UID have full access to each others' files. This has the same effect as sharing a login. There is no way to assure identification, authentication, and accountability because the system sees them as the same user. If the duplicate UID is 0, this gives potential intruders another privileged account to attack.
Fix
Edit user accounts to provide unique UIDs for each account.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000020: The system must require authentication upon booting into single-user and maintenance modes.
Ensure the root account for any bootable partitions has a password assigned in the /etc/security/passwd file.
Discussion
If the system does not require a valid root password before it boots into single-user or maintenance mode, anyone who invokes single-user or maintenance mode is granted privileged access to all files on the system.
Fix
Assign a root account password for any bootable partition.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005040: All FTP users must have a default umask of 077.
Check the umask setting for the "ftp" user. Procedure: # lsuser -a umask ftp If the umask value does not return 077 or 77, this is a finding. Check the default umask that the ftpd daemon is running with # grep ftpd /etc/inetd.conf If there is not a -u077 argument on the ftpd, this is a finding.
Discussion
The umask controls the default access mode assigned to newly created files. An umask of 077 limits new files to mode 700 or less permissive. Although umask is stored as a 4-digit number, the first digit representing special access modes is typically ignored or required to be zero (0).
Fix
Add the arguments -u077 to the ftpd on the /etc/inetd.conf and refresh inetd. #vi /etc/inetd.conf #refresh -s inetd Change the umask of the ftp user. #chuser umask=077 ftp
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003620: A separate file system must be used for user home directories (such as /home or equivalent).
Determine if the /home path is a separate file system. #df -k /home If /home is not on its own file system, this is a finding.
Discussion
The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.
Fix
Migrate the /home (or equivalent) path onto a separate file system.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003252: The at.deny file must have mode 0640 or less permissive.
Determine the mode of the at.deny file. # ls -lL /var/adm/cron/at.deny If the mode of the at.deny file is more permissive than 0640, this is a finding.
Discussion
The at daemon control files restrict access to scheduled job manipulation and must be protected. Unauthorized modification of the at.deny file could result in Denial of Service to authorized at users or provide unauthorized users with the ability to run at jobs.
Fix
Change the mode of the at.deny file to 0640. # chmod 0640 /var/adm/cron/at.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000300: All accounts on the system must have unique user or account names.
Perform the following to ensure there are no duplicate account names: # usrck -n ALL If any duplicate account names are found, this is a finding.
Discussion
A unique user name is the first part of the identification and authentication process. If user names are not unique, there can be no accountability on the system for auditing purposes. Multiple accounts sharing the same name could result in the Denial of Service to one or both of the accounts or unauthorized access to files or privileges.
Fix
Change user account names, or delete accounts, so each account has a unique name.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004420: Files executed through a mail aliases file must have mode 0755 or less permissive.
Find the aliases file on the system. Procedure: # find / -name aliases -depth -print Examine the aliases file for any directories or paths that may be utilized. Procedure: # more <aliases file location> Check the permissions for any paths referenced. Procedure: # ls -lL <path> If any file referenced from the aliases file has a mode more permissive than 0755, this is a finding.
Discussion
If a file executed through a mail alias file has permissions greater than 0755, it can be modified by an unauthorized user and may contain malicious code or instructions possibly compromising the system.
Fix
Use the chmod command to change the access permissions for files executed from the alias file. For example: # chmod 0755 < filename >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005522: The SSH public host key files must have mode 0644 or less permissive.
Check the permissions for SSH public host key files. # ls -lL /etc/ssh/*key.pub If any file has a mode more permissive than 0644, this is a finding.
Discussion
If a public host key file is modified by an unauthorized user, the SSH service may be compromised.
Fix
Change the permissions for the SSH public host key files. # chmod 0644 /etc/ssh/*key.pub
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002717: System audit tool executables must have mode 0750 or less permissive.
Determine if system audit tool executables have a mode more permissive than 0750. If any do, this is a finding. Audit tools include, but are not limited to, audit, auditcat, auditconv, auditpr, auditselect, auditstream, auditbin, and auditmerge.
Discussion
To prevent unauthorized access or manipulation of system audit logs, the tools for manipulating those logs must be protected.
Fix
Many audit tools have SUID bit set. Before changing permissions on system audit tool executables, check the file permissions for SUID bits. Change the mode of system audit tool executables to 0750. #chmod 0750 or 4750 <system audit tool executable> Document all changes made.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN008420: The system must use available memory address randomization techniques.
Running the sedmgr command without any options will show the settings currently in effect. #sedmgr If the value returned for the sedmgr mode is off, this is a finding.
Discussion
Successful exploitation of buffer overflow vulnerabilities relies in some measure to having a predictable address structure of the executing program. Address randomization techniques reduce the probability of a successful exploit.
Fix
Configure the system to use any available memory address randomization techniques. Recommended settings are either to enable stack execution disablement for all suid files or select system executables. Set sedmgr to enforce on selected files and terminate processes violating stack execution boundaries. # sedmgr -m select -o off OR Set sedmgr to enforce on setid files and terminate processes violating stack execution boundaries. # sedmgr -m setidfiles -o off After a global system change to the sed, the system should be rebooted. # shutdown -Fr
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000640: The system must require that passwords contain at least one special character.
Check the minother setting. Procedure: # grep minother /etc/security/user OR # lsuser -a minother ALL If the minother setting is less than 1, this is a finding.
Discussion
To enforce the use of complex passwords, minimum numbers of characters of different classes are mandated. The use of complex passwords reduces the ability of attackers to successfully obtain valid passwords using guessing or exhaustive search techniques. Complexity requirements increase the password search space by requiring users to construct passwords from a larger character set than they may otherwise use.
Fix
Use the chsec command to set the minother setting to 1. # chsec -f /etc/security/user -s default -a minother=1 # chuser minother=1 < user id >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000510: The system must display a publicly-viewable pattern during a graphical desktop environment session lock.
Determine if a publicly-viewable pattern is displayed during a session lock. If the session lock pattern is not publicly-viewable, this is a finding.
Discussion
To protect the on-screen content of a session, it must be replaced with a publicly-viewable pattern upon session lock. Examples of publicly viewable patterns include screen saver patterns, photographic images, solid colors, or a blank screen, so long as none of those patterns convey sensitive information. This requirement applies to graphical desktop environments provided by the system to locally attached displays and input devices, as well as, to graphical desktop environments provided to remote systems using remote access protocols.
Fix
Configure the system to display a publicly-viewable pattern during a session lock.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN005200: X displays must not be exported to the world.
If X Windows is not used on the system, this is not applicable. Check the output of the xhost command from an X terminal. Procedure: $ xhost If the output reports access control is enabled (and possibly lists the hosts that can receive X Window logins), this is not a finding. If the xhost command returns a line indicating access control is disabled, this is a finding. NOTE: It may be necessary to define the display if the command reports it cannot open the display. Procedure: $ DISPLAY=MachineName:0.0; export DISPLAY MachineName may be replaced with an Internet Protocol Address. Repeat the check procedure after setting the display.
Discussion
Open X displays allow an attacker to capture keystrokes and to execute commands remotely. Many users have their X Server set to xhost +, permitting access to the X Server by anyone, from anywhere.
Fix
If using an xhost-type authentication the xhost - command can be used to remove current trusted hosts and then selectively allow only trusted hosts to connect with xhost + commands. A cryptographically secure authentication, such as provided by the xauth program, is always preferred. Refer to your X11 server's documentation for further security information.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN003540: The system must implement non-executable program stacks.
On 64-bit systems, verify the sed_config (Stack Execution Disable) setting is "all". # lsattr -El sys0 -a sed_config If the second field is not "all", this is a finding. (32-bit systems do not support sed_config. This is a permanent finding on 32-bit AIX systems.)
Discussion
A common type of exploit is the stack buffer overflow. An application receives, from an attacker, more data than it is prepared for and stores this information on its stack, writing beyond the space reserved for it. This can be designed to cause execution of the data written on the stack. One mechanism to mitigate this vulnerability is for the system to not allow the execution of instructions in sections of memory identified as part of the stack.
Fix
Change the sed_config setting to disable stack execution for all processes. # chdev -l sys0 -a sed_config=all To assess the impact of updating sed_config, the "all+monitor" setting may be used temporarily. This temporary update does not mitigate the finding. Reboot the system for the new setting to take effect.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002140: All shells referenced in /etc/passwd must be listed in the /etc/shells file, except any shells specified for the purpose of preventing logins.
Confirm the login shells referenced in the /etc/passwd file are listed in the /etc/security/login.cfg file's shells =variable in the usw stanza. # more /etc/security/login.cfg # more /etc/shells The /usr/bin/false, /bin/false, /dev/null, /sbin/nologin, (and equivalents), and sdshell will be considered valid shells for use in the /etc/passwd file, but will not be listed in the shells stanza. If a shell referenced in /etc/passwd is not listed in the shells stanza, excluding the above mentioned shells, then this is a finding.
Discussion
The shells file lists approved default shells. It helps provide layered defense to the security approach by ensuring users cannot change their default shell to an unauthorized shell that may not be secure.
Fix
Use the chsh utility or edit the /etc/passwd file and correct the error by changing the default shell of the account in error to an acceptable shell name contained in the /etc/shells file. Alternatively, use the SMIT to change the /etc/passwd shell entry.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005533: The SSH daemon must limit connections to a single session.
Check the SSH daemon configuration for the MaxSessions setting. # grep -i MaxSessions /etc/ssh/sshd_config | grep -v '^#' If the setting is not present, or not set to 1, this is a finding.
Discussion
The SSH protocol has the ability to provide multiple sessions over a single connection without reauthentication. A compromised client could use this feature to establish additional sessions to a system without consent or knowledge of the user. Alternate per-connection session limits may be documented if needed for a valid mission requirement. Greater limits are expected to be necessary in situations where TCP or X11 forwarding are used.
Fix
Edit the SSH daemon configuration and add or edit the MaxSessions setting value to 1.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN006080: The Samba Web Administration Tool (SWAT) must be restricted to the local host or require SSL.
Check the system for an enabled SWAT service. # grep -i swat /etc/inetd.conf If SWAT is found enabled, it must be utilized with SSL to ensure a secure connection between the client and the server. Ask the SA to identify the method used to provide SSL protection for the SWAT service. Verify (or ask the SA to demonstrate) this configuration is effective by accessing SWAT using an HTTPS connection from a web browser. If SWAT is found enabled and has no SSL protection, this is a finding.
Discussion
SWAT is a tool used to configure Samba. As it modifies Samba configuration, which can impact system security, it must be protected from unauthorized access. SWAT authentication may involve the root password, which must be protected by encryption when traversing the network. Restricting access to the local host allows for the use of SSH TCP forwarding, if configured, or administration by a web browser on the local system.
Fix
Disable SWAT (e.g., remove the "swat" line from inetd.conf or equivalent, and restart the service) or configure SSL protection for the SWAT service.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001902: Local initialization files' lists of preloaded libraries must contain only absolute paths.
Verify local initialization files have library preload list containing only absolute paths. Procedure: # cat /etc/passwd | cut -f 1,1 -d ":" | xargs -n1 -IUSER sh -c "grep -l LDR_PRELOAD ~USER/.*" This variable is formatted as a colon-separated list of paths. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a finding.
Discussion
The library preload list environment variable contains a list of libraries for the dynamic linker to load before loading the libraries required by the binary. If this list contains paths to libraries relative to the current working directory, unintended libraries may be preloaded. This variable is formatted as a space-separated list of libraries. Paths starting with a slash (/) are absolute paths.
Fix
Edit the local initialization file and remove the relative path entry from the library preload variable LDR_PRELOAD.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000440: Successful and unsuccessful logins and logouts must be logged.
Determine if successful logons are being logged. # last | more Determine if unsuccessful logons are being logged. # last -f /etc/security/failedlogin | more If the commands do not return successful and unsuccessful logins, this is a finding.
Discussion
Monitoring and recording successful and unsuccessful logins assists in tracking unauthorized access to the system. Without this logging, the ability to track unauthorized activity to specific user accounts may be diminished.
Fix
Edit /etc/syslog.conf and add local log destinations for auth.* or both auth.notice and auth.info. "auth.info /var/log/authlog" Verify service startup scripts for syslog and utmp (if present) are enabled. # vi /etc/rc.tcpip Check the syslogd service is not commented out. Refresh syslogd. #refresh -s syslogd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003623: The system must use a separate file system for the system audit data path.
Determine the location of the audit data path. #more /etc/security/audit/config Make note of the binfile and trail location. (The best practice is to have the audit data and trails sent to /audit.) # cd < audit path > #df -k . If the system audit data path is not on a separate file system, this is a finding.
Discussion
The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.
Fix
Migrate the system audit data path onto a separate file system. Update the /etc/security/audit/config file as necessary to reflect the location of the audit data.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003360: The at daemon must not execute group-writable or world-writable programs.
List the "at" jobs on the system. Procedure: # ls -la /var/spool/cron/atjobs /var/spool/atjobs For each "at" job file, determine which programs are executed. Procedure: # more <at job file> Check each program executed by "at" for group- or world-writable permissions. Procedure: # ls -la <at program file> If "at" executes group- or world-writable programs, this is a finding.
Discussion
If the at facility executes world-writable or group-writable programs, it is possible for the programs to be accidentally or maliciously changed or replaced without the owner's intent or knowledge. This would cause a system security breach.
Fix
Remove group-write and world-write permissions from files executed by "at" jobs. Procedure: # chmod go-w <file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005180: All .Xauthority files must have mode 0600 or less permissive.
Check the file permissions for the .Xauthority files in the home directories of users of X. Procedure: # cd ~<X user> # ls -lL .Xauthority If the file mode is more permissive than 0600, this is finding.
Discussion
.Xauthority files ensure the user is authorized to access the specific X Windows host. Excessive permissions may permit unauthorized modification of these files, which could lead to Denial of Service to authorized access or allow unauthorized access to be obtained.
Fix
Change the mode of the .Xauthority files. Procedure: # chmod 0600 .Xauthority
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000520: The root user must not own the logon session for an application requiring a continuous display.
If there is an application running on the system continuously in use (such as a network monitoring application), ask the SA what the name of the application is. Execute the following to determine which user owns the process(es) associated with the application. If the owner is root, this is a finding. # ps -ef | more
Discussion
If an application is providing a continuous display and is running with root privileges, unauthorized users could interrupt the process and gain root access to the system.
Fix
Configure the system so the owner of a session requiring a continuous screen display, such as a network management display, is not root. Ensure the display is also located in a secure, controlled access area. Document and justify this requirement. Ensure the terminal and keyboard for the display (or workstation) are secure from all but authorized personnel by maintaining them in a secure area, in a locked cabinet where a swipe card, or other positive forms of identification, must be used to gain entry.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005380: If the system is a Network Management System (NMS) server, it must only run the NMS and any software required by the NMS.
Ask the SA if this is an NMS server. If it is an NMS server, then ask what other applications run on it. If there is anything other than network management software and DBMS software used only for the storage and inquiry of NMS data, this is a finding.
Discussion
Installing extraneous software on a system designated as a dedicated Network Management System (NMS) server poses a security threat to the system and the network. Should an attacker gain access to the NMS through unauthorized software, the entire network may be susceptible to malicious activity.
Fix
Ensure only authorized software is loaded on a designated NMS server. Authorized software is limited to the NMS software itself, a database management system for the NMS server if necessary, and network management software.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009190: The system must not have the comsat service active.
Check the /etc/inetd.conf file for active comsat service. #grep comsat /etc/inetd.conf | grep -v \# If the comsat service is enabled, this is a finding.
Discussion
The comsat daemon notifies users on incoming email. This is an unnecessary service and is vulnerable to a flood attack. Running unnecessary services increases the attack vector of the system.
Fix
Edit /etc/inetd.conf and comment out comsat service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006420: NIS maps must be protected through hard-to-guess domain names.
Check the domain name for NIS maps. Procedure: # domainname If the name returned is simple to guess, such as the organization name, building, or room name, etc., this is a finding.
Discussion
The use of hard-to-guess NIS domain names provides additional protection from unauthorized access to the NIS directory information.
Fix
Change the NIS domain name to a value difficult to guess. Consult vendor documentation for the required procedure.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001368: The /etc/hosts file must have mode 0644 or less permissive.
Check the mode of the /etc/hosts file. Procedure: # ls -l /etc/hosts If the file mode is more permissive than 0644, this is a finding.
Discussion
The /etc/hosts file (or equivalent) configures local host name to IP address mappings that typically take precedence over DNS resolution. If this file is maliciously modified, it could cause the failure or compromise of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.
Fix
Change the mode of the /etc/hosts file to 0644 or less permissive. # chmod 0644 /etc/hosts
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007900: The system must use an appropriate reverse-path filter for IPv6 network traffic, if the system uses IPv6.
Determine if the system is configured to use reverse-path filtering. Examine the IPSec rules on the system. # lsfilt -a All systems must block inbound traffic destined to the loopback address from other network interfaces. Additionally, if the system is multihomed and the attached networks are isolated or perform symmetric routing, traffic with source addresses expected on one interface must be blocked when received on another interface. If filtering is not configured on the system, this is a finding.
Discussion
Reverse-path filtering provides protection against spoofed source addresses by causing the system to discard packets that have source addresses for which the system has no route or if the route does not point towards the interface on which the packet arrived. Depending on the role of the system, reverse-path filtering may cause legitimate traffic to be discarded and, therefore, should be used with a more permissive mode or filter, or not at all. Whenever possible, reverse-path filtering should be used.
Fix
Configure the system to use reverse-path filtering using IP Sec filters. Add rules to block traffic with loopback network source addresses from being received on interfaces other than the loopback, such as other ethernet interfaces. Use smitty or genfilt command to block loopback address from network interfaces. # smitty ipsec6 # genfilt -v6 -a D -s <source address> -m <source netmask> -d <destination address> -M <Destination mask> -c all -o any -O any -p 0 -P 0 -w I -l y -a en0 If the system is multihomed and the attached networks are isolated or perform symmetric routing, add rules to block traffic with source addresses expected on one interface when received on another interface. # smitty ipsec6
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005900: The nosuid option must be enabled on all NFS client mounts.
Check the system for NFS mounts not using the nosuid option. Procedure: # lsfs -v nfs If the mounted file systems do not have the nosuid option, this is a finding.
Discussion
Enabling the nosuid mount option prevents the system from granting owner or group-owner privileges to programs with the suid or sgid bit set. If the system does not restrict this access, users with unprivileged access to the local system may be able to acquire privileged access by executing suid or sgid files located on the mounted NFS file system.
Fix
Edit /etc/filesystems and add the nosuid option for all NFS file systems. Remount the NFS file systems to make the change take effect.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005400: The /etc/syslog.conf file must be owned by root.
Check /etc/syslog.conf ownership. # ls -lL /etc/syslog.conf If /etc/syslog.conf is not owned by root, this is a finding.
Discussion
If the /etc/syslog.conf file is not owned by root, unauthorized users could be allowed to view, edit, or delete important system messages handled by the syslog facility.
Fix
Use the chown command to set the owner to root. # chown root /etc/syslog.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001860: All local initialization files must be owned by the user or root.
NOTE: The following commands must be run in the BASH shell. Check the ownership of local initialization files. Procedure (using a shell that supports ~USER as USER's home directory): # cut -d : -f 1 /etc/passwd | xargs -n1 -IUSER sh -c "ls -l ~USER/.[a-z]*" # cut -d : -f 1 /etc/passwd | xargs -n1 -IUSER find ~USER/.dt ! -fstype nfs ! -user USER -exec ls -ld {} \; If local initialization files are not owned by the home directory's user, this is a finding.
Discussion
Local initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.
Fix
Change the ownership of the startup and login files in the user's directory to the user or root, as appropriate. Examine each user's home directory and verify all file names beginning with "." are owned by the owner of the directory or root. If they are not, use the chown command to change the owner to the user and research the reasons why the owners were not assigned as required. Procedure: # chown username .filename Document all changes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003760: The services file must be owned by root or bin.
Check the ownership of the services file. Procedure: # ls -lL /etc/services If the services file is not owned by root or bin, this is a finding.
Discussion
Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the ownership of the services file to root or bin. Procedure: # chown root /etc/services
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005240: The .Xauthority utility must only permit access to authorized hosts.
Check the X Window system access is limited to authorized clients. Procedure: # xauth xauth> list Ask the SA if the clients listed are authorized. If any are not, this is a finding.
Discussion
If unauthorized clients are permitted access to the X server, a user's X session may be compromised.
Fix
Remove unauthorized clients from the xauth configuration. # xauth remove <display name>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005306: The SNMP service must require the use of a FIPS 140-2 approved cryptographic hash algorithm as part of its authentication and integrity methods.
Check all SNMPv3 users for configured authentication protocols. # grep USM_USER /etc/snmpdv3.conf The 4th field contains the hash used in the authentication protocol. If an entry exists that does not use HMAC-SHA for the authentication protocol, this is a finding.
Discussion
The SNMP service must use SHA-1 or a FIPS 140-2 approved successor for authentication and integrity.
Fix
Edit the /etc/snmpdv3.conf file. Change any instances of the HMAC-MD5 authentication protocol in USM_USER entries to HMAC-SHA. For all changed USM_USER entries, regenerate authentication keys using the "pwtokey" command and replace the keys in the /etc/snmpdv3.conf file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003900: The hosts.lpd file (or equivalent) must not contain a "+" character.
Look for the presence of a print service configuration file. Procedure: # find /etc -name hosts.lpd -print # find /etc -name Systems -print # find /etc -name printers.conf If none of the files are found, this check should be marked not applicable. Otherwise, examine the configuration file. Procedure: # more <print service file> Check for entries containing a "+" character by itself on any line. If any are found, this is a finding.
Discussion
Having the "+" character in the hosts.lpd (or equivalent) file allows all hosts to use local system print resources.
Fix
Remove the "+" entries from the hosts.lpd (or equivalent) file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005220: .Xauthority or X*.hosts (or equivalent) file(s) must be used to restrict access to the X server.
Determine if the X server is running. Procedure: # ps -ef |grep X Determine if xauth is being used. Procedure: # xauth xauth> list If the above command sequence does not show any host other than the localhost, then xauth is not being used. Search the system for an X*.hosts files, where * is a display number that may be used to limit X window connections. If no files are found, X*.hosts files are not being used. If the X*.hosts files contain any unauthorized hosts, this is a finding. If both xauth and X*.hosts files are not being used, this is a finding.
Discussion
If access to the X server is not restricted, a user's X session may be compromised.
Fix
Create an X*.hosts file, where * is a display number that may be used to limit X window connections. Add the list of authorized X clients to the file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000244: The system must use time sources local to the enclave.
Check the root crontab for ntpdate entries. # crontab -l | grep ntpdate If the ntpdate command is invoked with NTP servers outside of the enclave, this is a finding. Check the NTP daemon configuration. # grep '^server' ntp.conf If an NTP server is listed outside of the enclave, this is a finding.
Discussion
A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. The network architecture should provide multiple time servers within an enclave providing local service to the enclave and synchronize with time sources outside of the enclave. If this server is an enclave time server, this requirement is not applicable. If the system is completely isolated (no connections to networks or other systems), time synchronization is not required as no correlation of events or operation of time-dependent protocols between systems will be necessary. If the system is completely isolated, this requirement is not applicable.
Fix
If using ntpdate, remove NTP servers external to the enclave from the cron job running ntpdate. If using the NTP daemon, remove the server line from ntp.conf for each NTP server external to the enclave.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000000-AIX00060: A baseline of AIX files with the TCB bit set must be checked weekly.
Perform the following command with no parameters to ensure the system is in trusted mode. # /bin/tcbck If TCB is not installed, the output will show an error code of 3001-101 and/or a text message indicating TCB is not installed. If the output from the command indicates it is not in trusted mode, this is not reviewed. Otherwise, check the root crontab to verify tcbck is executed weekly. If it is not in the crontab, ask the SA if the check is run manually and to see the results of the check.
Discussion
If a baseline of files with the TCB bit set is not kept and checked weekly, the system could be compromised without the knowledge of any authority.
Fix
Add tcbck command as a weekly cronjob with the output sent to the SA.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003340: The at.allow file must have mode 0640 or less permissive.
Check the mode of the at.allow file. # ls -lL /var/adm/cron/at.allow If the at.allow file has a mode more permissive than 0640, this is a finding.
Discussion
Permissions more permissive than 0640 may allow unauthorized or malicious access to the at.allow and/or at.deny files.
Fix
Change the mode of the at.allow file. # chmod 0640 /var/adm/cron/at.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006040: The system must not have any peer-to-peer file-sharing application installed.
Ask the SA if any peer-to-peer file-sharing applications are installed. Some examples of these applications include: - Napster, - Kazaa, - ARES, - Limewire, - IRC Chat Relay, and - BitTorrent. If any of these applications are installed, this is a finding.
Discussion
Peer-to-peer file-sharing software can result in the unintentional exfiltration of information. There are also many legal issues associated with these types of utilities including copyright infringement or other intellectual property issues. The ASD Memo "Use of Peer-to-Peer (P2P) File-Sharing Applications across the DoD" states the following: “P2P file-sharing applications are authorized for use on DoD networks with approval by the appropriate Designated Approval Authority (DAA). Documented requirements, security architecture, configuration management process, and a training program for users are all requirements within the approval process. The unauthorized use of application or services, including P2P applications, is prohibited, and such applications or services must be eliminated.” P2P applications include, but are not limited to, the following: -Napster, -Kazaa, -ARES, -Limewire, -IRC Chat Relay, and -BitTorrent.
Fix
Uninstall the peer-to-peer file sharing application(s) from the system.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004460: The system syslog service must log informational and more severe SMTP service messages.
Check the syslog configuration file for mail.crit logging configuration. The syslog.conf file critical mail logging option line will typically appear as one of the following examples: mail.crit /var/log/syslog *.crit /var/log/syslog mail.* /var/log/syslog Procedure: # more /etc/syslog.conf If syslog is not configured to log critical Sendmail messages, this is a finding.
Discussion
If informational and more severe SMTP service messages are not logged, malicious activity on the system may go unnoticed.
Fix
Edit the syslog.conf file and add a configuration line specifying an appropriate destination for mail.crit syslogs.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006310: The /etc/news/nnrp.access file must not have an extended ACL.
Check the permissions of the file. # find / -name nnrp.access # ls -lL < nnrp.access > If extended permissions are enabled, this is a finding.
Discussion
File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. Excessive permissions on the nnrp.access file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.
Fix
Remove the extended ACL from the nnrp.access file. # acledit < nnrp.access >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000252: The time synchronization configuration file (such as /etc/ntp.conf) must have mode 0640 or less permissive.
Determine the mode of the ntp.conf file. # ls -l /etc/ntp.conf If the mode is more permissive than 0640, this is a finding.
Discussion
A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. If an illicit time source is used for synchronization, the integrity of system logs and the security of the system could be compromised. If the configuration files controlling time synchronization are not protected, unauthorized modifications could result in the failure of time synchronization.
Fix
Change the mode of the ntp.conf file to 0640 or less permissive. # chmod 0640 /etc/ntp.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007480: The Reliable Datagram Sockets (RDS) protocol must be disabled or not installed unless required.
AIX has RDS protocol installed as part of the 'bos.net.tcp.client' fileset. The RDS protocol in primarily used for communication on INFI-Band interfaces. The protocol is manually loaded with the bypassctrl command. Determine if RDS is currently loaded. #genkex | grep rds If the RDS protocol is loaded, ask the SA if RDS is required by application software running on the system. If so, this is not applicable. If the RDS protocol is loaded and the protocol is not used by application software, this is a finding.
Discussion
The Reliable Datagram Sockets (RDS) protocol is a relatively new protocol developed by Oracle for communication between the nodes of a cluster. Binding this protocol to the network stack increases the attack surface of the host. Unprivileged local processes may be able to cause the system to dynamically load a protocol handler by opening a socket using the protocol.
Fix
Configure the system to not automatically load the RDS protocol handler. Check startup scripts for 'bypassctrl load rds' and comment out the bypassctrl commands. Unload the driver from the kernel. # bypassctrl unload rds
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003800: Inetd or xinetd logging/tracing must be enabled.
Determine if inetd or xinetd has logging or tracing enabled. # ps -ef |grep inetd |grep -e "-d" If no results are returned, this is a finding.
Discussion
Inetd or xinetd logging and tracing allows the system administrators to observe the IP addresses that are connecting to their machines and to observe what network services are being sought. This provides valuable information when trying to find the source of malicious users and potential malicious users.
Fix
Edit the inetd startup script to contain the "-d" parameter for the inetd process. #vi /etc/rc.tcpip # chssys -s inetd -a '-d'
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001060: The system must log successful and unsuccessful access to the root account.
Check the following log files to determine if access to the root account is being logged. Try to su - and enter an incorrect password. # more /var/adm/sulog If root login accounts are not being logged, this is a finding.
Discussion
If successful and unsuccessful logins and logouts are not monitored or recorded, access attempts cannot be tracked. Without this logging, it may be impossible to track unauthorized access to the system.
Fix
Troubleshoot the system logging configuration to provide for logging of root account login attempts.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008600: The system must be configured to only boot from the system boot device.
Determine if the system is configured to boot from devices other than the system startup media. # bootlist -m normal -o The returned values should be hdisk{x}. If the system is setup to boot from a non-hard disk device, this is a finding. Additionally, ask the SA if the machine is setup for multi-boot in the SMS application. If multi-boot is enabled, the firmware will stop at boot time and request which image to boot from the user. If multi-boot is enabled, this is a finding.
Discussion
The ability to boot from removable media is the same as being able to boot into single user, or maintenance, mode without a password. This ability could allow a malicious user to boot the system and perform changes that could compromise or damage the system. It could also allow the system to be used for malicious purposes by a malicious anonymous user.
Fix
Configure the system to only boot from system startup media. # bootlist -m normal hdisk< x > Set multi-boot to off in the SMS application.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN001374: The /etc/nsswitch.conf file must not have an extended ACL.
Verify /etc/nsswitch.conf has no extended ACL. AIX does not use the /etc/nsswitch.conf file. This check is not applicable. Procedure: # aclget /etc/nsswitch.conf If extended permissions are enabled, this is a finding.
Discussion
The nsswitch.conf file (or equivalent) configures the source of a variety of system security information including account, group, and host lookups. Malicious changes could prevent the system from functioning or compromise system security.
Fix
Remove the extended ACL from the /etc/nsswitch.conf file. # acledit /etc/nsswitch.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002360: Audio devices must be group-owned by root, sys, bin, or system.
Check the group owner of audio devices. Procedure: # /usr/sbin/lsdev -C | grep -i audio # ls -lL /dev/*aud0 If the group owner of an audio device is not root, sys, bin, or system, this is a finding.
Discussion
Without privileged group owners, audio devices will be vulnerable to being used as eaves-dropping devices by malicious users or intruders to possibly listen to conversations containing sensitive information.
Fix
Change the group owner of the audio device. Procedure: # chgrp system <audio device>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001379: The /etc/passwd file must be group-owned by bin, security, sys, or system.
Check the group ownership of the password file. Procedure: # ls -lL /etc/passwd If the file is not group-owned by security, bin, sys, or system, this is a finding.
Discussion
The /etc/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification.
Fix
Change the group owner of the /etc/passwd file to security, bin, sys, or system. Procedure: # chgrp security /etc/passwd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008120: If the system is using LDAP for authentication or account information, the /etc/ldap.conf (or equivalent) file must not have an extended ACL.
Check the permissions of the /etc/security/ldap/ldap.cfg file. Procedure: # aclget /etc/security/ldap/ldap.cfg Check to see if extended permissions are enabled. If extended permissions are enabled, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Remove the extended ACL from the /etc/security/ldap/ldap.cfg file. # acledit /etc/security/ldap/ldap.cfg Disable extended file permissions.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004370: The aliases file must be group-owned by sys, bin, or system.
Check the group ownership of the /etc/mail/aliases file. Procedure: # ls -lL /etc/mail/aliases If the file is not group-owned by sys, bin, or system, this is a finding.
Discussion
If the alias file is not group-owned by a system group, an unauthorized user may modify the file to add aliases to run malicious code or redirect e-mail.
Fix
Change the group owner of the /etc/mail/aliases file. Procedure: # chgrp system /etc/mail/aliases
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004480: The SMTP service log file must be owned by root.
Locate any mail log files by checking the syslog configuration file. Procedure: # more /etc/syslog.conf Identify any log files configured for the mail service at any severity level, or those configured for all services. Check the ownership of these log files. Procedure: # ls -lL <file location> If any mail log file is not owned by root, this is a finding.
Discussion
If the SMTP service log file is not owned by root, then unauthorized personnel may modify or delete the file to hide a system compromise.
Fix
Change the ownership of the Sendmail log file. # chown root <sendmail log file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003621: The system must use a separate file system for /var.
Determine if the /var path is a separate file system. # df -k /var If /var is not on its own file system, this is a finding.
Discussion
The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.
Fix
Migrate the /var path onto a separate file system.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000580: The system must require passwords to contain a minimum of 14 characters.
Check the system password length setting. # /usr/sbin/lsuser -a minlen ALL If minlen is not set to 14 or more, this is a finding.
Discussion
The use of longer passwords reduces the ability of attackers to successfully obtain valid passwords using guessing or exhaustive search techniques by increasing the password search space.
Fix
Change the minimum password length to 14 or more. # chsec -f /etc/security/user -s default -a minlen=14 # chuser minlen=14 <user id>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009260: The system must not have the talk or ntalk services active.
Check the /etc/inetd.conf file for talk and ntalk services. #grep talk /etc/inetd.conf | grep -v \# If any TCP or UDP talk or ntalk services are enabled, this is a finding.
Discussion
The talk and ntalk commands allow users on the same or different systems on converse. The talk daemons are started from the inetd process and run as root. These unnecessary processes increase the attack vector of the system and may cause Denial of Service by scrambling the users display.
Fix
Edit /etc/inetd.conf and comment out TCP and UDP for the talk service. Edit /etc/inetd.conf and comment out TCP and UDP for the ntalk service. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003820: The rsh daemon must not be running.
# grep -v "^#" /etc/inetd.conf |grep rshd If rshd is found to be enabled, this is a finding.
Discussion
The rshd process provides a typically unencrypted, host-authenticated remote access service. SSH should be used in place of this service.
Fix
Edit /etc/inetd.conf and comment out the rshd service. Restart the inetd service.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN003660: The system must log authentication informational data.
Check /etc/syslog.conf and verify the auth facility is logging both the notice and info level messages by using one of the procedures below. # grep "auth.notice" /etc/syslog.conf # grep "auth.info" /etc/syslog.conf OR # grep 'auth.*' /etc/syslog.conf If auth.* is not found, and either auth.notice or auth.info is not found, this is a finding.
Discussion
Monitoring and recording successful and unsuccessful logins assists in tracking unauthorized access to the system.
Fix
Edit /etc/syslog.conf and add local log destinations for auth.* or both auth.notice and auth.info.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0320: The /etc/ftpaccess.ctl file must be owned by root.
Check the ownership of the /etc/ftpaccess.ctl file. # ls -l /etc/ftpaccess.ctl If the ftpaccess.ctl file is not owned by root, this is a finding.
Discussion
If the ftpaccess.ctl file is not owned by root, an unauthorized user may modify the file to allow unauthorized access to change the file. Unauthorized modification could result in Denial of Service to authorized FTP users or permit unauthorized access to system information.
Fix
Change the owner of the ftpaccess.ctl file to root. # chown root /etc/ftpaccess.ctl
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005350: Management Information Base (MIB) files must not have extended ACLs.
Check the file permissions for the MIB files. # find / -name *.mib -print # aclget [mib file] If the extended attributes are not disabled, this is a finding.
Discussion
The ability to read the MIB file could impart special knowledge to an intruder or malicious user about the ability to extract compromising information about the system or network.
Fix
Remove the extended ACL from the MIB file(s) and change extended attributes to disabled. #acledit [mib file]
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001372: The /etc/nsswitch.conf file must be group-owned by root, bin, sys, or system.
Check the group ownership of the nsswitch.conf file. AIX does not use the /etc/nsswitch.conf file. This check is not applicable. Procedure: # ls -lL /etc/nsswitch.conf If the file is not group-owned by root, bin, sys, or system, this is a finding.
Discussion
The nsswitch.conf file (or equivalent) configures the source of a variety of system security information including account, group, and host lookups. Malicious changes could prevent the system from functioning or compromise system security.
Fix
Change the group owner of the /etc/nsswitch.conf file to root, bin, sys, or system. Procedure: # chgrp system /etc/nsswitch.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001378: The /etc/passwd file must be owned by root.
Verify the /etc/passwd file is owned by root. Procedure: # ls -l /etc/passwd If the file is not owned by root, this is a finding.
Discussion
The /etc/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification.
Fix
Change the owner of the /etc/passwd file to root. # chown root /etc/passwd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001500: All interactive users' home directories must be owned by their respective users.
Check the ownership of each user's home directory listed in the /etc/passwd file. Procedure: # ls -lLd <user home directory> If any user's home directory is not owned by the assigned user, this is a finding.
Discussion
If users do not own their home directories, unauthorized users could access user files.
Fix
Change the owner of a user's home directory to its assigned user. Procedure: # chown <user> <home directory>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006620: The system's access control program must be configured to grant or deny system access to specific hosts.
Check for the existence of the /etc/hosts.allow and /etc/hosts.deny files. Procedure: # ls -la /etc/hosts.allow # ls -la /etc/hosts.deny If either file does not exist, this is a finding. Check for the presence of a default deny entry. Procedure: # grep "ALL: ALL" /etc/hosts.deny If the "ALL: ALL" entry is not present in the /etc/hosts.deny file, any TCP service from a host or network not matching other rules will be allowed access. If the entry is not in /etc/hosts.deny, this is a finding.
Discussion
If the system's access control program is not configured with appropriate rules for allowing and denying access to system network resources, services may be accessible to unauthorized hosts.
Fix
Edit the /etc/hosts.allow and /etc/hosts.deny files to configure access restrictions.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001020: The root account must not be used for direct logins.
Check if the root is used for direct logins. Procedure: # last root | grep -v reboot If any direct login records for root exist, this is a finding.
Discussion
Direct login with the root account prevents individual user accountability. Acceptable non-routine uses of the root account for direct login are limited to emergency maintenance, the use of single-user mode for maintenance, and situations where individual administrator accounts are not available.
Fix
Enforce policy requiring all root account access is attained by first logging into a user account and then becoming root (using su, for example).
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005770: The NFS exports configuration file must not have an extended ACL.
# aclget /etc/exports If the extended attributes are not disabled, this is a finding.
Discussion
File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. Excessive permissions on the NFS export configuration file could allow unauthorized modification of the file, which could result in Denial of Service to authorized NFS exports and the creation of additional unauthorized exports.
Fix
Remove the extended ACL from the NFS export configuration file and change extended attributes to disabled. #acledit /etc/exports
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001393: The /etc/group file must have mode 0644 or less permissive.
Check the mode of the /etc/group file. Procedure: # ls -l /etc/group If the file mode is more permissive than 0644, this is a finding.
Discussion
The /etc/group file is critical to system security and must be protected from unauthorized modification. The group file contains a list of system groups and associated information.
Fix
Change the mode of the /etc/group file to 0644 or less permissive. # chmod 0644 /etc/group
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005537: The SSH daemon must use privilege separation.
Check the SSH daemon configuration for the UsePrivilegeSeparation setting. # grep -i UsePrivilegeSeparation /etc/ssh/sshd_config | grep -v '^#' If the setting is present and set to "no", this is a finding. If the setting is not present or is set to "yes", this is not a finding.
Discussion
SSH daemon privilege separation causes the SSH process to drop root privileges when not needed, which would decrease the impact of software vulnerabilities in the unprivileged section.
Fix
Edit the /etc/ssh/sshd_config file and remove the UsePrivilegeSeparation setting or change the value of the UsePrivilegeSeparation setting to "yes".
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001440: All interactive users must be assigned a home directory in the /etc/passwd file.
Use usrck to verify home directory assignments are present. Procedure: # usrck -n ALL If any user is not assigned a home directory, this is a finding.
Discussion
If users do not have a valid home directory, there is no place for the storage and control of files they own.
Fix
Assign a home directory to any user without one.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000920: The root account's home directory (other than /) must have mode 0700.
Check the mode of the root home directory. Procedure: # grep "^root" /etc/passwd | awk -F":" '{print $6}' # ls -ld <root home directory> If the mode of the directory is not equal to 0700, this is a finding. If the home directory is /, this is not applicable.
Discussion
Permissions greater than 0700 could allow unauthorized users access to the root home directory.
Fix
The root home directory will have permissions of 0700. Do not change the protections of the / directory. Use the following command to change protections for the root home directory. # chmod 0700 /root.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004360: The alias file must be owned by root.
Check the ownership of the alias file. Procedure: # ls -lL /etc/mail/aliases If the file is not owned by root, this is a finding.
Discussion
If the alias file is not owned by root, an unauthorized user may modify the file to add aliases to run malicious code or redirect email.
Fix
Change the owner of the /etc/mail/aliases file (or equivalent, such as /usr/lib/aliases) to root. Procedure: # chown root /etc/mail/aliases
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001760: All global initialization files must be group-owned by sys, bin, system, or security.
Check the group ownership of global initialization files. Procedure: # ls -lL /etc/.login /etc/profile /etc/bashrc /etc/environment /etc/security/environ /etc/security/.profile /etc/csh.login /etc/csh.cshrc If any global initialization file is not group-owned by sys, bin, system, or security, this is a finding.
Discussion
Global initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the group ownership of the global initialization file(s) with incorrect group ownership. Procedure: # chgrp system <global initialization file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003604: The system must not respond to ICMP timestamp requests sent to a broadcast address.
# /usr/sbin/no -o bcastping If the value returned is not 0, this is a finding.
Discussion
The processing of Internet Control Message Protocol (ICMP) timestamp requests increases the attack surface of the system. Responding to broadcast ICMP timestamp requests facilitates network mapping and provides a vector for amplification attacks.
Fix
Configure the system to ignore ICMP Timestamp requests sent to broadcast addresses. #no -po bcastping=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003320: Default system accounts (with the exception of root) must not be listed in the at.allow file or must be included in the at.deny file if the at.allow file does not exist.
# more /var/adm/cron/at.allow If default accounts (such as bin, sys, adm, and others) are listed in the at.allow file, this is a finding.
Discussion
Default accounts, such as bin, sys, adm, uucp, daemon, and others, should never have access to the at facility. This would create a possible vulnerability open to intruders or malicious users.
Fix
Remove the default accounts (such as bin, sys, adm, and others) from the at.allow file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005100: The TFTP daemon must have mode 0755 or less permissive.
Check the mode of the TFTP daemon. Procedure: # find / -name "*tftpd" -print # ls -lL <file location> If the mode of the file is more permissive than 0755, this is a finding.
Discussion
If TFTP runs with the setuid or setgid bit set, it may be able to write to any file or directory and may seriously impair system integrity, confidentiality, and availability.
Fix
Change the mode of the TFTP daemon. Procedure: # chmod 0755 <tftp server>
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN007850: The DHCP client must not send dynamic DNS updates.
Determine if the system's DHCP client is configured to send dynamic DNS updates. #grep "^updateDNS" /etc/dhcpc.opt /etc/dhcpcd.ini If any lines are returned, this is a finding.
Discussion
Dynamic DNS updates transmit unencrypted information about a system including its name and address and should not be used unless needed.
Fix
Configure the system's DHCP client to not send dynamic DNS updates. Remove / comment updateDNS lines from the /etc/dhcpcd.ini and /etc/dhcpc.opt files.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000980: The system must prevent the root account from directly logging in except from the system console.
Check the remote login ability of the root account. Procedure: # lsuser -a rlogin root If the rlogin value is not false, this is a finding.
Discussion
Limiting the root account direct logins to only system consoles protects the root account from direct unauthorized access from a non-console device.
Fix
The root account can be protected from non-console device logins by setting rlogin = false in the root: stanza of the /etc/security/user file. #chsec -f /etc/security/user -s root -a rlogin=false
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000242: The system must use at least two time sources for clock synchronization.
Check the system for a running NTP daemon. # ps -ef | grep ntp Verify the auto-startup of xntpd in /etc/rc.tcpip. # cat /etc/rc.tcpip | grep -v "^#" Verify at least two external NTP servers are listed in the /etc/ntp.conf file. # cat /etc/ntp.conf | grep -v "^#" | grep -i server | egrep -v "127.127.1.1|127.127.1.0" If xntpd is not invoked with at least two external NTP servers listed (127.127.1.0 or 127.127.1.1 are local clock references and therefore not allowed), this is a finding.
Discussion
A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. For redundancy, two time sources are required so synchronization continues to function if one source fails. If the system is completely isolated (no connections to networks or other systems), time synchronization is not required as no correlation of events or operation of time-dependent protocols between systems will be necessary. If the system is completely isolated, this requirement is not applicable. NOTE: For the Network Time Protocol (NTP), the requirement is two servers, but it is recommended to configure at least four distinct time servers which allow NTP to effectively exclude a time source not consistent with the others. The system's local clock must be excluded from the count of time sources.
Fix
If auto-starting xntpd, add (when necessary) the correct number of (at least two) external servers to the /etc/ntp.conf file. If using ntpdate, add additional NTP servers (at least two are required) to the cron job running ntpdate.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004820: Anonymous FTP must not be active on the system unless authorized.
Attempt to log into this host with a user name of anonymous and a password of guest (also try the password of [email protected]). If the logon is successful, this is a finding. Procedure: # ftp localhost Name: anonymous 530 Guest login not allowed on this machine.
Discussion
Due to the numerous vulnerabilities inherent in anonymous FTP, it is recommended that it not be used. If anonymous FTP must be used on a system, the requirement must be authorized and approved in the system accreditation package.
Fix
Remove user "anonymous" from /etc/passwd.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000251: The time synchronization configuration file (such as /etc/ntp.conf) must be group-owned by bin, sys, or system.
Check the group ownership of the NTP configuration file. Procedure: # ls -lL /etc/ntp.conf If the group owner is not bin, sys, or system, this is a finding.
Discussion
A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. If an illicit time source is used for synchronization, the integrity of system logs and the security of the system could be compromised. If the configuration files controlling time synchronization are not owned by a system group, unauthorized modifications could result in the failure of time synchronization.
Fix
Change the group owner of the NTP configuration file. Procedure: # chgrp system /etc/ntp.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000402: The Department of Defense (DoD) login banner must be displayed immediately prior to, or as part of, graphical desktop environment login prompts.
Access the graphical desktop environment(s) provided by the system and attempt to logon. Check for either of the following login banners based on the character limitations imposed by the system. An exact match is required. If one of these banners is not displayed, this is a finding. "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details. " OR "I've read & consent to terms in IS user agreem't."
Discussion
Failure to display the login banner prior to a logon attempt will negate legal proceedings resulting from unauthorized access to system resources. This requirement applies to graphical desktop environments provided by the system to locally attached displays and input devices, as well as, to graphical desktop environments provided to remote systems, including thin clients.
Fix
Edit the Xresources file to configure the system to display one of the DoD login banners (based on the character limitations imposed by the system) prior to, or as part of, the graphical desktop environment login process. For Dt login, change the variable Dtlogin*greeting.labelString: in Xresources file. #cp /usr/dt/config/C/Xresources /etc/dt/config/C/Xresources #vi /etc/dt/config/C/Xresources For XDM login, change the variable Xlogin*greeting in the Xresources file. #vi /usr/lpp/X11/lib/X11/xdm/Xresources. DoD Login Banners: "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details. " OR "I've read & consent to terms in IS user agreem't."
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008020: If the system is using LDAP for authentication or account information, the LDAP TLS connection must require the server provide a certificate and this certificate has a valid trust path to a trusted CA.
Check if the system is using LDAP authentication. #grep LDAP /etc/security/user If no lines are returned, this vulnerability is not applicable. Verify SSL is enabled. #grep '^useSSL' /etc/security/ldap/ldap.cfg If yes is not the returned value, this is a finding. Verify a server certificate is required and verified by the LDAP configuration. #grep -I '^ldapsslkeyf' /etc/security/ldap/ldap.cfg Make note of the key database file location. #gsk7cmd -cert -list CA -db <certificate keyfile.kdb> -pw <Password> Make note of the Key Label. #gsk7cmd -cert -details -showOID -db <certificate key.kdb> -pw <Password> -label <Key Label> THE IBM GSK Database should only have certificates for the client system and for the LDAP server. If more certificates are in the key database than the LDAP server and the client, this is a finding.
Discussion
The NSS LDAP service provides user mappings which are a vital component of system security. Communication between an LDAP server and a host using LDAP for NSS require authentication.
Fix
Install a certificate signed by a DoD PKI or a DoD-approved external PKI. #gsk7cmd < or > ikeyman Remove un-needed CA certificates. #gsk7cmd < or > ikeyman
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003790: The services file must not have an extended ACL.
Check the permissions of the /etc/services file. #aclget /etc/services Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
The services file is critical to the proper operation of network services and must be protected from unauthorized modification. If the services file has an extended ACL, it may be possible for unauthorized users to modify the file. Unauthorized modification could result in the failure of network services.
Fix
Remove the extended ACL from the services file and disable extended permissions. #acledit /etc/services
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000850: The system must restrict the ability to switch to the root user to members of a defined group.
Examine the sugroups of the root user. Generally only users in the adm group should have su to root capacity. Procedure: #lsuser -a sugroups root If this is blank or ALL, this is a finding.
Discussion
Configuring a supplemental group for users permitted to switch to the root user prevents unauthorized users from accessing the root account, even with knowledge of the root credentials.
Fix
Use the chsec command to only allow users in the adm group to su to root. #chsec -f /etc/security/user -s root -a sugroups=adm
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN008160: If the system is using LDAP for authentication or account information, the TLS certificate authority file and/or directory (as appropriate) must be group-owned by root, bin, sys, or system.
Check the group ownership of the SSL key database file. Determine the location of the SSL key database. # grep -i '^ldapsslkeyf' /etc/security/ldap/ldap.cfg Check the group ownership of the SSL key database file. # ls -lLa <ldap certificate file(s) or directories> If a certificate file or directory is not group-owned by root, bin, security, sys, or system, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Change the group ownership of LDAP client SSL certificate database file to root, security, bin, sys, or system. Procedure: # chgrp system < certificate file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000940: The root account's executable search path must be the vendor default and must contain only absolute paths.
To view the root user's PATH, log in as the root user, and execute the following. # env | grep PATH This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon or two consecutive colons, this is a finding. If an entry starts with a character other than a slash (/), this is a finding. If directories beyond those in the vendor's default root path are present, this is a finding.
Discussion
The executable search path (typically the PATH environment variable) contains a list of directories for the shell to search to find executables. If this path includes the current working directory or other relative paths, executables in these directories may be executed instead of system commands. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon or two consecutive colons, this is interpreted as the current working directory. Entries starting with a slash (/) are absolute paths.
Fix
Edit the root user's local initialization files. Change any found PATH variable settings to the vendor's default path for the root user. Remove any empty path entries or references to relative paths. # cd <root's home directory> # vi .profile .cshrc If the bash shell is installed, edit these additional files. # vi .bashrc .bash_profile
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001391: The /etc/group file must be owned by root.
Verify the /etc/group file is owned by root. Procedure: # ls -l /etc/group If the file is not owned by root, this is a finding.
Discussion
The /etc/group file is critical to system security and must be owned by a privileged user. The group file contains a list of system groups and associated information.
Fix
Change the owner of the /etc/group file to root. # chown root /etc/group
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009310: The system must not have the rusersd service active.
Check the /etc/inetd.conf file for active rusersd service. #grep rusersd /etc/inetd.conf | grep -v \# If the rusersd service is enabled, this is a finding.
Discussion
The rusersd daemon gives out a list of current uses on the system. The rusersd daemon is unnecessary and it increases the attack vector of the system by providing information on the current users of the system.
Fix
Edit the /etc/inetd.conf file and comment out the rusersd service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007840: The DHCP client must be disabled if not needed.
If the DHCP client is needed by the system, this is not applicable. Determine if the DHCP client is disabled. # ps -ef |grep dhcpcd If dhcpcd is running, this is a finding.
Discussion
DHCP allows for the unauthenticated configuration of network parameters on the system by exchanging information with a DHCP server.
Fix
Disable the system's DHCP client. Edit /etc/rc.tcpip, comment out the line starting dhcpcd. Reboot the system to ensure the DHCP client has been disabled fully. Configure a static IP for the system, if network connectivity is required.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007780: The system must not have 6to4 enabled.
Determine if there are any 6to4 tunnels configured on the system. #ifconfig -a If there are any sit or cit adapters in the ifconfig listing, this is a finding.
Discussion
6to4 is an IPv6 transition mechanism involving tunneling IPv6 packets encapsulated in IPv4 packets on an ad-hoc basis. This is not a preferred transition strategy and increases the attack surface of the system.
Fix
Remove the configuration for any 6to4 tunnels on the system. #ifconfig sit0 detach #rmdev -dl sit0 #ifconfig cit0 detach #rmdev -dl cit0 Set the startup script /etc/rc.net to call autoconf6 with the -6 argument to prevent setting up 6 to 4 tunnels.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000880: The root account must be the only account having an UID of 0.
Check the system for duplicate UID 0 assignments by listing all accounts assigned UID 0. Procedure: # grep ":0:" /etc/passwd | awk -F":" '{print$1":"$3":"}' | grep ":0:" If any accounts other than root are assigned UID 0, this is a finding.
Discussion
If an account has an UID of 0, it has root authority. Multiple accounts with an UID of 0 afford more opportunity for potential intruders to guess a password for a privileged account.
Fix
Remove or change the UID of accounts other than root that have UID 0.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005390: The /etc/syslog.conf file must have mode 0640 or less permissive.
Check the permissions of the syslog configuration file. # ls -lL /etc/syslog.conf If the mode of the file is more permissive than 0640, this is a finding.
Discussion
Unauthorized users must not be allowed to access or modify the /etc/syslog.conf file.
Fix
Change the permissions of the syslog configuration file. # chmod 0640 /etc/syslog.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005375: The snmpd.conf file must not have an extended ACL.
Determine if the snmpd.conf file or equivalent has an extended ACL. Procedure: # find / -name "snmpd*.conf" # aclget < snmpd conf > If the extended attributes are not disabled, this is a finding.
Discussion
The snmpd.conf file contains authenticators and must be protected from unauthorized access and modification.
Fix
Remove the extended ACL from the snmpd.conf file (or equivalent) and change extended attributes to disabled. #acledit < snmpd conf >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001160: All files and directories must have a valid owner.
Check the system for files with no assigned owner. Procedure: # find / -nouser -print If any files have no assigned owner, this is a finding.
Discussion
Unowned files and directories may be unintentionally inherited if a user is assigned the same UID as the UID of the unowned files.
Fix
All directories and files (executable and data) will have an identifiable owner and group name. Either trace files to an authorized user, change the file's owner to root, or delete them. Determine the legitimate owner of the files and use the chown command to set the owner and group to the correct value. If the legitimate owner cannot be determined, change the owner to root (but make sure none of the changed files remain executable because they could be Trojan horses or other malicious code). Examine the files to determine their origin and the reason for their lack of an owner/group. #chown <a-valid-user> <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000950: The root account's list of preloaded libraries must be empty.
Verify the LDR_PRELOAD environment variable is empty or not defined for the root user. # env | grep LDR_PRELOAD If a path is returned, this is a finding.
Discussion
The library preload list environment variable contains a list of libraries for the dynamic linker to load before loading the libraries required by the binary. If this list contains paths to libraries relative to the current working directory, unintended libraries may be preloaded. This variable is formatted as a space-separated list of libraries. Paths starting with (/) are absolute paths.
Fix
Edit the root user's initialization files and remove any definition of LDR_PRELOAD.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005420: The /etc/syslog.conf file must be group-owned by bin, sys, or system.
Check /etc/syslog.conf group ownership. Procedure: # ls -lL /etc/syslog.conf If /etc/syslog.conf is not group-owned by sys, bin, or system, this is a finding.
Discussion
If the group owner of /etc/syslog.conf is not root, bin, or sys, unauthorized users could be permitted to view, edit, or delete important system messages handled by the syslog facility.
Fix
Change the group owner of the /etc/syslog.conf file to bin, sys, or system. Procedure: # chgrp system /etc/syslog.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009250: The system must not have the PostOffice Protocol (POP3) service active.
Check the '/etc/inetd.conf' file for active POP3 service. #grep pop3 /etc/inetd.conf | grep -v \# If the POP3 service is enabled, this is a finding.
Discussion
The POP3 service is only needed if the server is acting as a mail server and clients are using applications that only support POP3. Users' ids and passwords are sent in plain text to the POP3 service. If mail client access is needed, consider using IMAP or SSL enabled POP3.
Fix
Edit /etc/inetd.conf and comment out POP3 the service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006560: The system vulnerability assessment tool, host-based intrusion detection tool, and file integrity tool must notify the SA and the IAO of a security breach or a suspected security breach.
For each security tool on the system, determine if the tool is configured to notify the IAO and SA of any detected security problem. If such notifications are not configured, this is a finding.
Discussion
Timely notifications of potential security compromises minimize the potential damage. Minimally, the system must log these events and the SA and the IAO will receive the notifications during the daily system log review. If feasible, active alerting (such as email or paging) should be employed consistent with the site’s established operations management systems and procedures.
Fix
Configure the security tools on the system to notify the IAO and SA when any security issues are detected.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005280: The system must not have the UUCP service active.
# grep uucp /etc/inetd.conf If uucp is found enabled, this is a finding.
Discussion
The UUCP utility is designed to assist in transferring files, executing remote commands, and sending e-mail between UNIX systems over phone lines and direct connections between systems. The UUCP utility is a primitive and arcane system with many security issues. There are alternate data transfer utilities/products that can be configured to more securely transfer data by providing for authentication as well as encryption.
Fix
Edit /etc/inetd.conf and comment out the uucp service. Restart the inetd service.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001880: All local initialization files must have mode 0740 or less permissive.
Check the modes of local initialization files. Procedure: # ls -al /<usershomedirectory>/.login # ls -al /<usershomedirectory>/.cshrc # ls -al /<usershomedirectory>/.logout # ls -al /<usershomedirectory>/.profile # ls -al /<usershomedirectory>/.bash_profile # ls -al /<usershomedirectory>/.bashrc # ls -al /<usershomedirectory>/.bash_logout # ls -al /<usershomedirectory>/.env # ls -al /<usershomedirectory>/.dtprofile (permissions should be 0755) # ls -al /<usershomedirectory>/.dispatch # ls -al /<usershomedirectory>/.emacs # ls -al /<usershomedirectory>/.exrc # find /<usershomedirectory>/.dt ! -fstype nfs \( -perm -0002 -o -perm -0020 \) -exec ls -ld {} \; (permissions not to be more permissive than 0755) If local initialization files are more permissive than 0740, the .dt directory or the .dtprofile file is more permissive than 0755, this is a finding.
Discussion
Local initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.
Fix
Ensure user startup files have permissions of 0740 or more restrictive. Examine each user's home directory and verify all file names beginning with "." have access permissions of 0740 or more restrictive. If they do not, use the chmod command to correct the vulnerability. Procedure: # chmod 0740 .filename NOTE: The period is part of the file name and is required.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000140: A file integrity baseline must be created and maintained.
Determine if a file integrity baseline, which includes cryptographic hashes, has been created and maintained for the system. If no file integrity baseline exists for the system, this is a finding. If the file integrity baseline contains no cryptographic hashes, this is a finding. If the file integrity baseline is not maintained (has not been updated to be consistent with the latest approved system configuration changes), this is a finding.
Discussion
A file integrity baseline is a collection of file metadata which is to evaluate the integrity of the system. A minimal baseline must contain metadata for all device files, setuid files, setgid files, system libraries, system binaries, and system configuration files. The minimal metadata must consist of the mode, owner, group owner, and modification times. For regular files, metadata must also include file size and a cryptographic hash of the file’s contents.
Fix
Create a file integrity baseline, including cryptographic hashes, for the system. # find / -depth -print | tee Baseline Open the above file and either manually execute md5sum, csum, or the chksum command on each file. Alternatively, write a script to perform the above. NOTE: For security purposes, "md5sum" is preferred over "chksum". The md5sum command can be loaded from the Linux Tool Kit for AIX. Alternatively, OpenSSL can be used to create hashes. #openssl dgst -md5 < file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001850: Global initialization files' lists of preloaded libraries must contain only absolute paths.
Check the global initialization files' library preload list. # grep LDR_PRELOAD /etc/profile /etc/bashrc /etc/security/.login /etc/environment /etc/security/environ This variable is formatted as a colon-separated list of paths. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a relative path, and this is a finding.
Discussion
The library preload list environment variable contains a list of libraries for the dynamic linker to load before loading the libraries required by the binary. If this list contains paths to libraries relative to the current working directory, unintended libraries may be preloaded. This variable is formatted as a space-separated list of libraries. Paths starting with a slash (/) are absolute paths.
Fix
Edit the global initialization files and remove the relative path entry from the library preload list variable 'LDR_PRELOAD'.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002120: The /etc/shells (or equivalent) file must exist.
Check /etc/security/login.cfg for a shells stanza. Procedure: # grep -p usw: /etc/security/login.cfg | grep "shells =" If no such stanza exists, this is a finding. Check the /etc/shells file. Procedure: # more /etc/shells If the /etc/shells file does not exist, this is a finding.
Discussion
The shells file (or equivalent) lists approved default shells. It helps provide layered defense to the security approach by ensuring users cannot change their default shell to an unauthorized shell that may not be secure.
Fix
Edit the /etc/security/login.cfg file and add a shells stanza containing a list of valid shells. #chsec -f /etc/security/login.cfg -s usw -a shells=<list of approved shells> Create the /etc/shells file. #vi /etc/shells
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002340: Audio devices must be owned by root.
Check the owner of audio devices. Procedure: # /usr/sbin/lsdev -C | grep -i audio # ls -lL /dev/*aud0 If the owner of any audio device file is not root, this is a finding.
Discussion
Audio and video devices that are globally accessible have proven to be another security hazard. There is software that can activate system microphones and video devices connected to user workstations and/or X terminals. Once the microphone has been activated, it is possible to eavesdrop on otherwise private conversations without the victim being aware of it. This action effectively changes the user's microphone to a bugging device.
Fix
Change the owner of the audio device. # chown root <audio device>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003700: Inetd and xinetd must be disabled or removed if no network services utilizing them are enabled.
First, determine if inetd/xinetd is running. # ps -ef |grep inetd If inetd is not running, this is not a finding. # grep -v "^#" /etc/inetd.conf If no active services are found, yet the inetd daemon is running, this is a finding.
Discussion
Unnecessary services should be disabled to decrease the attack surface of the system.
Fix
Remove or disable the inetd startup scripts and kill the service.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002210: All shell files must be group-owned by root, bin, sys, or system.
Check the group ownership of each shell referenced. Procedure: # cat /etc/shells | xargs -n1 ls -l If any shell is not group owned by root, bin, sys, or system, this is a finding. #grep shells /etc/security/login.cfg | grep -v \* | cut -f 2 -d = | sed s/,/\ /g | xargs -n1 ls -l If any shell is not group owned by root, bin, sys, or system, this is a finding. Otherwise, check any shells found on the system. Procedure: # find / -name "*sh" | xargs -n1 ls -l If a shell is not group-owned by root, bin, sys, or system, this is a finding.
Discussion
If shell files are group-owned by users other than root or a system group, they could be modified by intruders or malicious users to perform unauthorized actions.
Fix
Change the group owner of the shell to root, bin, sys, or system. # chgrp system < shell >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000480: The delay between login prompts following a failed login attempt must be at least 4 seconds.
Check the logindelay parameter. # more /etc/security/login.cfg OR #grep logindelay /etc/security/login.cfg | grep -v \* Verify the value of the logindelay variable is 4 or more in each stanza. If the value of logindelay is not 4 or more, this is a finding.
Discussion
Enforcing a delay between successive failed login attempts increases protection against automated password guessing attacks.
Fix
Use vi or the chsec command to change the login delay time period. #chsec -f /etc/security/login.cfg -s default -a logindelay=4 OR # vi /etc/security/login.cfg Add logindelay = 4 to the default stanza.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001380: The /etc/passwd file must have mode 0644 or less permissive.
Check the mode of the /etc/passwd file. Procedure: # ls -lL /etc/passwd If /etc/passwd has a mode more permissive than 0644, this is a finding.
Discussion
If the password file is writable by a group owner or the world, the risk of password file compromise is increased. The password file contains the list of accounts on the system and associated information.
Fix
Change the mode of the passwd file to 0644. Procedure: # chmod 0644 /etc/passwd Document all changes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003260: The cron.deny file must be owned by root, bin, or sys.
# ls -lL /var/adm/cron/cron.deny If the cron.deny file is not owned by root, sys, or bin, this is a finding.
Discussion
Cron daemon control files restrict the scheduling of automated tasks and must be protected.
Fix
# chown root /var/adm/cron/cron.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002800: The audit system must be configured to audit login, logout, and session initiation.
Check the system's audit configuration. # more /etc/security/audit/events Confirm the following events are configured: USER_Login, USER_Logout, INIT_Start, INIT_End and USER_SU. If any of these events are not present, this is a finding. Check the USER_Login, USER_Logout, INIT_Start, INIT_End, and USER_SU audit events are defined in the audit classes' stanza 'classes:' of the /etc/security/audit/config file. #more /etc/security/audit/config Make note of the audit class(es) the USER_Login, USER_Logout, INIT_Start, INIT_End, and USER_SU events are associated with. If the USER_Login, USER_Logout, INIT_Start, INIT_End, and USER_SU events are not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. #more /etc/security/audit/config If the class(es) the USER_Login, USER_Logout, INIT_Start, INIT_End, and USER_SU events are not associated with the default user and all the system users in the users: stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Edit /etc/security/audit/events and add the USER_Login, USER_Logout, INIT_Start, INIT_End, and USER_SU events to the list of audited events. Edit /etc/security/audit/config and add the USER_Login, USER_Logout, INIT_Start, INIT_End, and USER_SU audit events to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes with the USER_Login, USER_Logout, INIT_Start, INIT_End, and USER_SU events to the all users listed in the users: stanza.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004940: The ftpusers file must have mode 0640 or less permissive.
Check the permissions of the ftpusers file. # ls -l /etc/ftpusers If the ftpusers file has a mode more permissive than 0640, this is a finding.
Discussion
Excessive permissions on the ftpusers file could permit unauthorized modification. Unauthorized modification could result in Denial of Service to authorized FTP users or permit unauthorized users to access the FTP service.
Fix
Change the mode of the ftpusers file to 0640. # chmod 0640 /etc/ftpusers
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005120: The TFTP daemon must be configured to vendor specifications, including a dedicated TFTP user account, a non-login shell, such as /bin/false, and a home directory owned by the TFTP user.
Check the /etc/passwd file to determine if TFTP is configured properly. Procedure: # grep tftp /etc/passwd If a TFTP user account does not exist and TFTP is active, this is a finding. Check the user shell for the TFTP user. If it is not /bin/false or equivalent, this is a finding. Check the home directory assigned to the TFTP user. If no home directory is set, or the directory specified is not dedicated to the use of the TFTP service, this is a finding.
Discussion
If TFTP has a valid shell, it increases the likelihood of someone logging to the TFTP account and compromising the system.
Fix
Create a TFTP user account if none exists. Assign a non-login shell to the TFTP user account, such as /bin/false. Assign a home directory to the TFTP user account.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000460: The system must disable accounts after three consecutive unsuccessful login attempts.
# /usr/sbin/lsuser -a loginretries ALL | more Check all active accounts on the system for the maximum number of tries before the system will lock the account. If a user has values set to 0 or greater then 3, this is a finding.
Discussion
Disabling accounts after a limited number of unsuccessful login attempts improves protection against password guessing attacks.
Fix
Use the chsec command to configure the number of unsuccessful logins resulting in account lockout. # chsec -f /etc/security/user -s default -a loginretries=3 # chsec -f /etc/security/user -s <user id> -a loginretries=3
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005538: The SSH daemon must not allow rhosts RSA authentication.
Check the SSH daemon configuration for the RhostsRSAAuthentication setting. # grep -i RhostsRSAAuthentication /etc/ssh/sshd_config | grep -v '^#' If the setting is present and set to "yes", this is a finding. If the setting is absent or set to "no", this is not a finding.
Discussion
If SSH permits rhosts RSA authentication, a user may be able to log in based on the keys of the host originating the request and not any user-specific authentication.
Fix
Edit the /etc/ssh/sshd_config file and remove the RhostsRSAAuthentication setting or change the value of the RhostsRSAAuthentication setting to "no".
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001362: The /etc/resolv.conf file must be owned by root.
Verify the /etc/resolv.conf file is owned by root. Procedure: # ls -l /etc/resolv.conf If the file is not owned by root, this is a finding.
Discussion
The resolv.conf (or equivalent) file configures the system's DNS resolver. DNS is used to resolve host names to IP addresses. If DNS configuration is modified maliciously, host name resolution may fail or return incorrect information. DNS may be used by a variety of system security functions, such as time synchronization, centralized authentication, and remote system logging.
Fix
Change the owner of the /etc/resolv.conf file to root. # chown root /etc/resolv.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003740: The inetd.conf and xinetd.conf files must have mode 0440 or less permissive.
Check the mode of inetd.conf file. # ls -lL /etc/inetd.conf If the mode of the file(s) is more permissive than 0440, this is a finding.
Discussion
The Internet service daemon configuration files must be protected as malicious modification could cause Denial of Service or increase the attack surface of the system.
Fix
Change the mode of the inetd.conf file. # chmod 0440 /etc/inetd.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001420: The /etc/security/passwd file must have mode 0400.
Check the mode of the /etc/security/passwd file. Procedure: # ls -lL /etc/security/passwd If the mode of this file is more permissive than 0400, this is a finding.
Discussion
The /etc/security/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification. The file also contains password hashes which must not be accessible to users other than root.
Fix
Change the mode of the /etc/security/passwd file. # chmod 0400 /etc/security/passwd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003140: Cron and crontab directories must be group-owned by system, sys, bin, or cron.
Check the group owner of cron and crontab directories. Procedure: # ls -ld /var/spool/cron/crontabs If a cron or crontab directory is not group-owned by sys, system, bin, or cron, this is a finding.
Discussion
To protect the integrity of scheduled system jobs and to prevent malicious modification to these jobs, crontab files must be secured. Failure to give group ownership of cron or crontab directories to a system group provides the designated group and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the group owner of the crontab directories to sys, system, bin, or cron. Procedure: # chown cron /var/spool/cron/crontabs
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005820: The NFS anonymous UID and GID must be configured to values without permissions.
Check if the anon option is set correctly for exported file systems. List exported file systems. # exportfs -v Each of the exported file systems should include an entry for the 'anon=' option set to -1 or an equivalent (60001, 60002, 65534, or 65535). If an appropriate 'anon=' setting is not present for an exported file system, this is a finding.
Discussion
When an NFS server is configured to deny remote root access, a selected UID and GID are used to handle requests from the remote root user. The UID and GID should be chosen from the system to provide the appropriate level of non-privileged access.
Fix
Edit /etc/exports and set the anon=-1 option for exported file systems without it. Re-export the file systems. # exportfs -a
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001640: Run control scripts must not execute world-writable programs or scripts.
Check the permissions on the files or scripts executed from system startup scripts to see if they are world-writable. Create a list of all potential run command level scripts. ls -l /etc/init.d/* | tr '\011' ' ' | tr -s ' ' | cut -f 9,9 -d " " Create a list of world writeable files. # find / -perm -002 -type f >> worldWriteableFileList Determine if any of the world writeable files in worldWriteableFileList are called from the run command level scripts. Note: Depending upon the number of scripts vs world writeable files, it may be easier to inspect the scripts manually. # more `ls -l /etc/init.d/* | tr '\011' ' ' | tr -s ' ' | cut -f 9,9 -d "` If any system startup script executes any file or script that is world-writable, this is a finding.
Discussion
World-writable files could be modified accidentally or maliciously to compromise system integrity.
Fix
Remove the world-writable permission from programs or scripts executed by run control scripts. Procedure: # chmod o-w <program or script executed from run control script>
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN001410: The /etc/security/passwd file must be group-owned by security, bin, sys, or system.
Check the ownership of the /etc/security/passwd file. Procedure: # ls -lL /etc/security/passwd If the file is not group-owned by security, bin, sys, or system, this is a finding.
Discussion
The /etc/security/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification. The file also contains password hashes which must not be accessible to users other than root.
Fix
Change the group owner of the /etc/security/passwd file to security, bin, sys, or system. Procedure: # chgrp security /etc/security/passwd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008000: If the system is using LDAP for authentication or account information, certificates used to authenticate to the LDAP server must be provided from DoD PKI or a DoD-approved external PKI.
Check if the system is using LDAP authentication. #grep LDAP /etc/security/user If no lines are returned, this vulnerability is not applicable. Check if the useSSL option is enabled. #grep '^useSSL' /etc/security/ldap/ldap.cfg If yes is not the returned value, this is a finding. Verify a certificate is used for client authentication to the server. #grep -I '^ldapsslkeyf' /etc/security/ldap/ldap.cfg If no line is found, this is a finding. List the certificate issuer with IBM GSK. #gsk7cmd -cert -list CA -db <certificate keyfile.kdb> -pw <Password> Make note of the client Key Label. #gsk7cmd -cert -details -showOID -db <certificate key.kdb> -pw <Password> -label <Key Label> If the certificate is not issued by DoD PKI or a DoD-approved external PKI, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. Communication between an LDAP server and a host using LDAP requires authentication.
Fix
Create a key database with DoD PKI or DoD-approved certificate. #gsk7cmd OR #ikeyman Edit /etc/security/ldap/ldap.conf and add or edit the ldapsslkeyf setting to reference a file containing a client certificate issued by DoD PKI or a DoD-approved external PKI.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002320: Audio devices must have mode 0660 or less permissive.
Check the mode of audio devices. # /usr/sbin/lsdev -C | grep -i audio # ls -lL /dev/*aud0 If the mode of audio devices are more permissive than 0660, this is a finding.
Discussion
Audio and video devices that are globally accessible have proven to be another security hazard. There is software that can activate system microphones and video devices connected to user workstations and/or X terminals. Once the microphone has been activated, it is possible to eavesdrop on otherwise private conversations without the victim being aware of it. This action effectively changes the user's microphone to a bugging device.
Fix
Change the mode of audio devices. # chmod o-w <audio device>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001360: The NIS/NIS+/yp files must have mode 0755 or less permissive.
Perform the following to check NIS file mode # ls -lRa /var/nis /var/yp /usr/lib/nis /usr/lib/netsvc/yp If the file's mode is more permissive than 0755, this is a finding.
Discussion
NIS/NIS+/yp files are part of the system's identification and authentication processes and are, therefore, critical to system security. Unauthorized modification of these files could compromise these processes and the system.
Fix
Change the mode of NIS/NIS+/yp files to 0755 or less permissive. Procedure (example): # chmod 0755 <filename>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005580: A system used for routing must not run other network services or applications.
Ask the SA if the system is a designated router. If it is not, this is not applicable. Check the system for non-routing network services. Procedure: # netstat -a | grep -i listen # ps -ef If non-routing services, including Web servers, file servers, DNS servers, or applications servers, but excluding management services, such as SSH and SNMP, are running on the system, this is a finding.
Discussion
Installing extraneous software on a system designated as a dedicated router poses a security threat to the system and the network. Should an attacker gain access to the router through the unauthorized software, the entire network is susceptible to malicious activity.
Fix
Ensure only authorized software is loaded on a designated router. Authorized software will be limited to the most current version of routing protocols and SSH for system administration purposes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000120: System security patches and updates must be installed and up-to-date.
Obtain the list of available security patches from IBM. Verify the available patches and service packs have been installed on the system. Check the currently running TL (Technology Levels and Service Packs). #oslevel -s Perform the following to obtain a list of installed patches. # /usr/sbin/instfix -i If there are security patches available and applicable for the system that have not been installed, this is a finding.
Discussion
Timely patching is critical for maintaining the operational availability, confidentiality, and integrity of Information Technology (IT) systems. However, failure to keep operating system and application software patched is a common mistake made by IT professionals. New patches are released daily, and it is often difficult for even experienced system administrators to keep abreast of all the new patches. When new weaknesses in an operating system exist, patches are usually made available by the vendor to resolve the problems. If the most recent security patches and updates are not installed, unauthorized users may take advantage of weaknesses present in the unpatched software. The lack of prompt attention to patching could result in a system compromise.
Fix
Use a web browser to access the vendor's support web site. Download the service packs and patches. Use SMIT to apply the updates. #smitty update_all
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003830: The rlogind service must not be running.
Determine if the rlogind service is running. If it is, this is a finding. # grep -v "^#" /etc/inetd.conf |grep rlogin If any results are returned, this is a finding
Discussion
The rlogind process provides a typically unencrypted, host-authenticated remote access service. SSH should be used in place of this service.
Fix
Disable the rlogind service out of the '/etc/inetd.conf' file. # vi /etc/inetd.conf Comment out the rlogind service. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001210: All system command files must not have extended ACLs.
Verify all system command files have no extended ACLs. # aclget /etc # aclget /bin # aclget /usr/bin # aclget /usr/lbin # aclget /usr/ucb # aclget /sbin # aclget /usr/sbin If any of the command files have extended permissions enabled, this is a finding.
Discussion
Restricting permissions will protect system command files from unauthorized modification. System command files include files present in directories used by the operating system for storing default system executables and files present in directories included in the system's default executable search paths.
Fix
Remove the extended ACL(s) from the system command file(s) and set the extended permissions to disabled. #acledit < command path >/< command file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007960: The ldd command must be disabled unless it protects against the execution of untrusted files.
Consult vendor documentation concerning the ldd command. If the command provides protection from the execution of untrusted executables, this is not a finding. Determine the location of the system's ldd command. Procedure: # find / -name ldd If no file exists, this is not a finding. Check the permissions of the found ldd file. # ls -lL <path to ldd> If the file mode of the file is more permissive than 0000, this is a finding.
Discussion
The ldd command provides a list of dependent libraries needed by a given binary, which is useful for troubleshooting software. Instead of parsing the binary file, some ldd implementations invoke the program with a special environment variable set, which causes the system dynamic linker to display the list of libraries. Specially crafted binaries can specify an alternate dynamic linker which may cause a program to be executed instead of examined. If the program is from an untrusted source, such as in a user home directory, or a file suspected of involvement in a system compromise, unauthorized software may be executed with the rights of the user running ldd. Some ldd implementations include protections preventing the execution of untrusted files. If such protections exist, this requirement is not applicable. An acceptable method of disabling ldd is changing its mode to 0000. The SA may conduct troubleshooting by temporarily changing the mode to allow execution and running the ldd command as an unprivileged user upon trusted system binaries.
Fix
Disable the ldd command by removing its permissions. Procedure: # chmod 0000 <path to ldd>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009240: The system must not have Internet Message Access Protocol (IMAP) service active.
Check the /etc/inetd.conf file for active IMAP service. #grep imapd /etc/inetd.conf | grep -v \# If the IMAP service is enabled, this is a finding.
Discussion
The IMAP service should not be running unless the system is acting as a mail server for client connections. Running unnecessary services increases the attack vector on the system.
Fix
Edit /etc/inetd.conf and comment out the imap2 service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003080: Crontab files must have mode 0600 or less permissive, and files in cron script directories must have mode 0700 or less permissive.
Check the modes of the crontab and cron job script files. If the mode is more permissive than 0600 for crontab files or 0700 for cron job script files, this is a finding.
Discussion
To protect the integrity of scheduled system jobs and prevent malicious modification to these jobs, crontab files must be secured.
Fix
Change the modes of crontab files to 0600 and cron job script files to 0700.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001820: All skeleton files and directories (typically in /etc/skel) must be owned by root or bin.
Check skeleton files ownership. Procedure: # ls -l /etc/security/.profile /etc/security/mkuser.sys If a skeleton file is not owned by root or bin, this is a finding.
Discussion
If the skeleton files are not protected, unauthorized personnel could change user startup parameters and possibly jeopardize user files. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the ownership of skeleton files with incorrect mode. # chown root /etc/security/.profile /etc/security/mkuser.sys
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005507: The SSH daemon must be configured to only use Message Authentication Codes (MACs) employing FIPS 140-2 approved cryptographic hash algorithms.
Check the SSH daemon configuration for allowed MACs. Procedure: # grep -i macs /etc/ssh/sshd_config | grep -v '^#' If no lines are returned, or the returned MACs list contains any MAC other than hmac-sha1, this is a finding.
Discussion
DoD information systems are required to use FIPS 140-2 approved cryptographic hash functions.
Fix
Edit the SSH daemon configuration and remove any MACs other than hmac-sha1. If necessary, add a MACs line.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006180: The /var/private/smbpasswd file must be group-owned by sys or system.
Check smbpasswd ownership. # ls -lL /var/private/smbpasswd If smbpasswd is not group-owned by sys, or system, this is a finding.
Discussion
If the smbpasswd file is not group-owned by root, the smbpasswd file may be maliciously accessed or modified, potentially resulting in the compromise of Samba accounts.
Fix
Use the chgrp command to change the group owner of the smbpasswd file to system. # chgrp system /var/private/smbpasswd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003210: The cron.deny file must not have an extended ACL.
#aclget /var/adm/cron/cron.deny Verify if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
If there are excessive file permissions for the cron.deny file, sensitive information could be viewed or edited by unauthorized users.
Fix
Remove the extended ACL from the cron.deny file and disable extended permissions. #acledit /var/adm/cron/cron.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000760: Accounts must be locked upon 35 days of inactivity.
Indications of inactive accounts are those without entries in the last log. Check the date in the last log to verify it is within the last 35 days. If an inactive account is not disabled via an invalid login shell /bin/false entry in the shell field of the /etc/passwd file or account_locked = true in /etc/security/user file, this is a finding.
Discussion
On some systems, accounts with disabled passwords still allow access using rcp, remsh, or rlogin through equivalent remote hosts. All that is required is the remote host name and the user name match an entry in a hosts.equiv file and have a .rhosts file in the user directory. Using a shell called /bin/false or /dev/null (or an equivalent) will add a layered defense. Non-interactive accounts on the system, such as application accounts, may be documented exceptions.
Fix
All inactive accounts will have /bin/false, /usr/bin/false, or /dev/null as the default shell in the /etc/passwd file and have the password disabled. Disable the inactive accounts. Examine the inactive accounts using the last command. Note the date of last login for each account. If any (other than system and application accounts) exceed 35 days, then disable them by placing a shell of /bin/false or /dev/null in the shell field of the passwd file entry for that account. An alternative, and preferable method, is to disable the account using SMIT or the chsec command. Change the accounts login shell. #chsh <account> /bin/false Lock the account in /etc/security/user file. #chuser account_locked=true < user id > OR # smitty chuser
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004800: Unencrypted FTP must not be used on the system.
Determine if unencrypted ftp or telnet are enabled. Procedure: # grep ftp /etc/inetd.conf # grep telnet /etc/inetd.conf If either of these services are found, and are active, ask the SA if they encrypted. If they are not, this is a finding.
Discussion
FTP is typically unencrypted and, therefore, presents confidentiality and integrity risks. FTP may be protected by encryption in certain cases, such as when used in a Kerberos environment. SFTP and FTPS are encrypted alternatives to FTP.
Fix
Edit /etc/inetd.conf and comment out or remove the ftp and telnet service lines. # vi /etc/inetd.conf Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003521: The kernel core dump data directory must be group-owned by bin, sys, or system.
Determine the core file copy location. #sysdumpdev -l | grep -i "core dir" Determine the group owner of the kernel core dump data directory. # ls -lLd < directory > If the group owner is not bin, sys, or system, this is a finding.
Discussion
Kernel core dumps may contain the full contents of system memory at the time of the crash. As the system memory may contain sensitive information, it must be protected accordingly. If the kernel core dump data directory is not group-owned by a system group, the core dumps contained in the directory may be subject to unauthorized access.
Fix
Change the group owner of the kernel core dump data directory to bin, sys, or system. # chgrp sys < directory >
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN005320: The snmpd.conf file must have mode 0600 or less permissive.
Check the mode of the SNMP daemon configuration file. Locate the SNMP daemon configuration file. Consult vendor documentation to verify the name and location of the file. Procedure: # find / -name "snmpd*.conf" Check the mode of the SNMP daemon configuration file. Procedure: # ls -lL <snmpd conf>
Discussion
The snmpd.conf file contains authenticators and must be protected from unauthorized access and modification.
Fix
Change the mode of the SNMP daemon configuration file to 0600. Procedure: # chmod 0600 /etc/snmpd.conf # chmod 0600 /etc/snmpdv3.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002380: The owner, group owner, mode, ACL, and location of files with the setuid bit set must be documented using site-defined procedures.
Files with the setuid bit set will allow anyone running these files to be temporarily assigned the user or group ID of the file. If an executable with setuid allows shell escapes, the user can operate on the system with the effective permission rights of the user or group owner. List all setuid files on the system. Procedure: # find / -perm -4000 -exec ls -l {} \; | more NOTE: Executing these commands may result in large listings of files; the output may be redirected to a file for easier analysis. Ask the SA or IAO if files with the setuid bit set have been documented. If any undocumented file has its setuid bit set, this is a finding.
Discussion
All files with the setuid bit set will allow anyone running these files to be temporarily assigned the UID of the file. While many system files depend on these attributes for proper operation, security problems can result if setuid is assigned to programs that allow reading and writing of files, or shell escapes. Only default vendor-supplied executables should have the setuid bit set.
Fix
Document the files with the setuid bit set or unset the setuid bit on the executable.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0350: The /etc/ftpaccess.ctl file must not have an extended ACL.
Check the permissions of the /etc/ftpaccess.ctl file. #aclget /etc/ftpaccess.ctl Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Excessive permissions on the ftpaccess.ctl file could permit unauthorized modification. Unauthorized modification could result in Denial of Service to authorized FTP users or permit unauthorized access to system information.
Fix
Remove the extended ACL from the /etc/ftpaccess.ctl file. #acledit /etc/ftpaccess.ctl Disable extended permissions.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005521: The SSH daemon must restrict login ability to specific users and/or groups.
Check the SSH daemon configuration for the AllowGroups setting. # grep -i AllowGroups /etc/ssh/sshd_config | grep -v '^#' If no lines are returned, this is a finding.
Discussion
Restricting SSH logins to a limited group of users, such as system administrators, prevents password-guessing and other SSH attacks from reaching system accounts and other accounts not authorized for SSH access.
Fix
Edit the SSH daemon configuration and add an AllowGroups directive.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001100: Root passwords must never be passed over a network in clear text form.
Determine if root has logged in over an unencrypted network connection. First, determine if root has logged in over a network. Procedure: # last | grep "^root " | egrep -v "reboot|console" | more Next, determine if the SSH daemon is running. Procedure: # ps -ef |grep sshd If root has logged in over the network and SSHD is not running, this is a finding.
Discussion
If a user accesses the root account (or any account) using an unencrypted connection, the password is passed over the network in clear text form and is subject to interception and misuse. This is true even if recommended procedures are followed by logging on to a named account and using the su command to access root.
Fix
Install OpenSSH from AIX installation media or AIX Expansion Pack. #smitty installp Enable SSH on the system and use it for all remote connections used to attain root access. Disable direct root login. # chsec -f /etc/security/user -s root -a rlogin=false
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN005450: The system must use a remote syslog server (log host).
Check the syslog configuration file for remote syslog servers. # grep '@' /etc/syslog.conf | grep -v '^#' If no line is returned, this is a finding.
Discussion
A syslog server (log host) receives syslog messages from one or more systems. This data can be used as an authoritative log source in the event a system is compromised and its local logs are suspect.
Fix
Edit the syslog configuration file and add an appropriate remote syslog server.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001610: Run control scripts' lists of preloaded libraries must contain only absolute paths.
Verify run control scripts' library preload list. This variable is formatted as a colon-separated list of paths. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a relative path, and this is a finding. # grep -r LDR_PRELOAD /etc/rc*
Discussion
The library preload list environment variable contains a list of libraries for the dynamic linker to load before loading the libraries required by the binary. If this list contains paths to libraries relative to the current working directory, unintended libraries may be preloaded. This variable is formatted as a space-separated list of libraries. Paths starting with a slash (/) are absolute paths.
Fix
Edit the run control scripts' library preload list and remove relative paths.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003624: The system must use a separate file system for /tmp (or equivalent).
Determine if the /tmp path is a separate file system. # df -k /tmp If /tmp is not its own file system, this is a finding.
Discussion
The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.
Fix
Migrate the /tmp path onto a separate file system.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN005140: Any active TFTP daemon must be authorized and approved in the system accreditation package.
Determine if the TFTP daemon is active. # grep -v "^#" /etc/inetd.conf |grep tftp If TFTP is found enabled, it is a finding if it is not documented using site-defined procedures.
Discussion
TFTP is a file transfer protocol often used by embedded systems to obtain configuration data or software. The service is unencrypted and does not require authentication of requests. Data available using this service may be subject to unauthorized access or interception.
Fix
Disable the TFTP daemon. Edit /etc/inetd.conf and comment out the tftp line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN005610: The system must not have IP forwarding for IPv6 enabled, unless the system is an IPv6 router.
# /usr/sbin/no -o ip6forwarding If the value returned is 1, this is a finding.
Discussion
If the system is configured for IP forwarding and is not a designated router, it could be used to bypass network security by providing a path for communication not filtered by network devices.
Fix
Disable IPv6 forwarding on the system. # /usr/sbin/no -p -o ip6forwarding=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001371: The /etc/nsswitch.conf file must be owned by root.
Verify the /etc/nsswitch.conf file is owned by root. AIX does not use the /etc/nsswitch.conf file. This check is not applicable. Procedure: # ls -l /etc/nsswitch.conf If the file is not owned by root, this is a finding.
Discussion
The nsswitch.conf file (or equivalent) configures the source of a variety of system security information including account, group, and host lookups. Malicious changes could prevent the system from functioning or compromise system security.
Fix
Change the owner of the /etc/nsswitch.conf file to root. # chown root /etc/nsswitch.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000241: The system clock must be synchronized continuously, or at least daily.
Check the root crontab for ntpdate jobs running at least daily. # crontab -l | grep ntpdate Columns 3, 4, and 5 must be an asterisk (*) for the job to be run daily. If this job exists, this is not a finding. OR Verify the auto-startup of xntpd in /etc/rc.tcpip. # cat /etc/rc.tcpip | grep -v "^#" Check the system for a running NTP daemon, which is the preferred method. # ps -ef | grep ntp If an (x)ntpd process exists, this is not a finding. Otherwise, this is a finding.
Discussion
A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. Internal system clocks tend to drift and require periodic resynchronization to ensure their accuracy. Software, such as ntpd, can be used to continuously synchronize the system clock with authoritative sources. Alternatively, the system may be synchronized periodically, with a maximum of one day between synchronizations. If the system is completely isolated (no connections to networks or other systems), time synchronization is not required as no correlation of events or operation of time-dependent protocols between systems will be necessary. If the system is completely isolated, this requirement is not applicable.
Fix
Enable the NTP daemon for continuous synchronization. Edit /etc/rc.tcpip and enable xntpd daemon. Edit /etc/ntp.conf and add the ntp server entry. # startsrc -s xntpd OR Add a daily or more frequent cronjob to perform synchronization using ntpdate. NOTE: While it is possible to run ntpdate from a cron script, it is important to mention that ntpdate with contrived cron scripts is no substitute for the NTP daemon, which uses sophisticated algorithms to maximize accuracy and reliability while minimizing resource use. Finally, since ntpdate polling does not discipline the host clock frequency as does xntpd, the accuracy using ntpdate is limited. The process of passively listening for NTP broadcasts (i.e., placing the line broadcastclient yes in the /etc/ntp.conf file) is preferred over any procedural form of direct server polling for a large network with many nodes needing to be time synchronized. This method is preferred because it significantly reduces the network traffic load related to NTP.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005000: Anonymous FTP accounts must not have a functional shell.
Check the shell for the anonymous FTP account. Procedure: # grep "^ftp" /etc/passwd This is a finding if the seventh field is empty (the entry ends with a ':') or if the seventh field does not contain one of the following. /bin/false /dev/null /usr/bin/false /bin/true /sbin/nologin
Discussion
If an anonymous FTP account has been configured to use a functional shell, attackers could gain access to the shell if the account is compromised.
Fix
Configure anonymous FTP accounts to use a non-functional shell. If necessary, edit the /etc/passwd file to remove any functioning shells associated with the FTP account and replace them with non-functioning shells, such as, /dev/null.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN001840: All global initialization files' executable search paths must contain only absolute paths.
Check the global initialization files' executable search paths. Procedure: # grep -i PATH /etc/profile /etc/bashrc /etc/csh.login /etc/csh.cshrc /etc/environment /etc/.login /etc/security/environ This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a relative path, and this is a finding.
Discussion
The executable search path (typically the PATH environment variable) contains a list of directories for the shell to search to find executables. If this path includes the current working directory or other relative paths, executables in these directories may be executed instead of system commands. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.
Fix
Edit the global initialization file(s) with PATH variables containing relative paths. Edit the file and remove the relative path from the PATH variable.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006270: The /etc/news/hosts.nntp file must not have an extended ACL.
Check the permissions of the hosts.nntp file. # find / -type f -name hosts.nntp # aclget < hosts.nntp file > If extended permissions are enabled, the file has an extended ACL, this is a finding.
Discussion
File system extended ACLs provide access to files beyond what is allowed by the numbers of the files. Excessive permissions on the hosts.nntp file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.
Fix
Remove the extended ACL from the hosts.nntp file. #acledit < hosts.nntp file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001310: All library files must not have extended ACLs.
Determine if any system library file has an extended ACL. If so, this is a finding. Check to see if extended permissions are disabled. If extended permissions are not disabled, this is a finding. #aclget < directory >/< file >
Discussion
Unauthorized access could destroy the integrity of the library files.
Fix
Remove the extended ACL(s) from the system library file(s) and disable extended permissions. #acledit < directory >/< file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008060: If the system is using LDAP for authentication or account information the /etc/ldap.conf (or equivalent) file must have mode 0644 or less permissive.
Check the permissions of the /etc/security/ldap/ldap.cfg file. # ls -lL /etc/security/ldap/ldap.cfg If the mode of the file is more permissive than 0644, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Change the permissions of the /etc/security/ldap/ldap.cfg file to 0644 or less permissive. # chmod 0644 /etc/security/ldap/ldap.cfg
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007940: The system must not accept source-routed IPv6 packets.
# /usr/sbin/no -o ipsrcrouterecv If the value returned is not 0, this is a finding.
Discussion
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the handling of source-routed traffic destined to the system itself, not to traffic forwarded by the system to another, such as when IPv6 forwarding is enabled and the system is functioning as a router.
Fix
Configure the system to not accept source-routed IPv6 packets. # /usr/sbin/no -p -o ipsrcrouterecv=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002100: The .rhosts file must not be supported in PAM.
Check the PAM configuration for rhosts_auth. Procedure: # grep rhosts_auth /etc/pam.conf |grep -v \# If a rhosts_auth entry is found, this is a finding.
Discussion
The .rhosts files are used to specify a list of hosts permitted remote access to a particular account without authenticating. The use of such a mechanism defeats strong identification and authentication requirements.
Fix
Edit /etc/pam.conf and remove the reference(s) to the rhosts_auth module.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007760: Proxy Neighbor Discovery Protocol (NDP) must not be enabled on the system.
If the system does not support proxy NDP, this is not applicable. Determine if the system has proxy NDP enabled. If IPv6 is enabled, determine if any non-local published NDP entries exist on the system. # ndp -a If any NDP entries contain non-local published entries, this is a finding.
Discussion
Proxy Neighbor Discovery Protocol (NDP) allows a system to respond to NDP requests on one interface on behalf of hosts connected to another interface. If this function is enabled when not required, addressing information may be leaked between the attached network segments.
Fix
Remove non-local published NDP entries from the system. # ndp -d <host> Check system startup scripts for commands publishing NDP entries (such as "ndp -s <int> <host> <hwaddr> pub") and remove them.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001590: All run control scripts must have no extended ACLs.
Verify run control scripts have no extended ACLs. Check if extended permissions are disabled. # ls -l /etc/rc* # aclget /etc/rc* # aclget /etc/init.d If extended permissions are not disabled, this is a finding.
Discussion
If the startup files are writable by other users, they could modify the startup files to insert malicious commands into the startup files.
Fix
Remove the extended ACL from the run control script(s) and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002480: Public directories must be the only world-writable directories and world-writable files must be located only in public directories.
Check the system for world-writable files and directories. Procedure: # find / -perm -2 -a \( -type d -o -type f \) -exec ls -ld {} \; If any world-writable files or directories are located, except those required for proper system or application operation, such as /tmp and /dev/null, this is a finding.
Discussion
World-writable files and directories make it easy for a malicious user to place potentially compromising files on the system. The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage (e.g., /tmp) and for directories requiring global read/write access.
Fix
Remove or change the mode for any world-writable file or directory on the system that is not required to be world-writable. Procedure: # chmod o-w <file/directory> Document all changes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006100: The /usr/lib/smb.conf file must be owned by root.
Check the ownership of the /usr/lib/smb.conf file. Procedure: # ls -l /usr/lib/smb.conf If an smb.conf file is not owned by root, this is a finding.
Discussion
The /usr/lib/smb.conf file allows access to other machines on the network and grants permissions to certain users. If it is owned by another user, the file may be maliciously modified and the Samba configuration could be compromised.
Fix
Change the ownership of the smb.conf file. Procedure: # chown root /usr/lib/smb.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006120: The /usr/lib/smb.conf file must be group-owned by bin, sys, or system.
Check the group ownership of the smb.conf file. Procedure: # ls -l /usr/lib/smb.conf If an smb.conf file is not group-owned by bin, sys, or system, this is a finding.
Discussion
If the group-owner of the smb.conf file is not root or a system group, the file may be maliciously modified and the Samba configuration could be compromised.
Fix
Change the group owner of the smb.conf file. Procedure: # chgrp system /usr/lib/smb.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006300: The /etc/news/nnrp.access (or equivalent) must have mode 0600 or less permissive.
Check /etc/news/nnrp.access permissions. # find / -name nnrp.access # ls -lL < nnrp.access > If /etc/news/nnrp.access has a mode more permissive than 0600, this is a finding.
Discussion
Excessive permissions on the nnrp.access file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.
Fix
Change the mode of the nnrp.access file to 0600. # chmod 0600 < nnrp.access >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009290: The system must not have the systat service active.
Check the /etc/inetd.conf file for active systat service. #grep systat /etc/inetd.conf | grep -v \# If the systat service is enabled, this is a finding.
Discussion
The systat daemon allows remote users to see the running process and who is running them. This may aid in information collection for an attack and weaken the security posture of the system.
Fix
Edit /etc/inetd.conf and comment out systat the service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0110: The /etc/netsvc.conf file must not have an extended ACL.
Verify there is no extended ACL on the /etc/netsvc.conf file. # aclget /etc/netsvc.conf If extended permissions are enabled, this is a finding.
Discussion
The /etc/netsvc.conf file is used to specify the ordering of name resolution for the sendmail command, alias resolution for the sendmail command, and host name resolution routines. Malicious changes could prevent the system from functioning correctly or compromise system security.
Fix
Remove the extended ACL from the /etc/nsswitch.conf file and disable extended permissions. #acledit /etc/netsvc.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009120: The system, if capable, must be configured to require the use of a CAC, PIV compliant hardware token, or Alternate Logon Token (ALT) for authentication.
Consult vendor documentation to determine if the system is capable of CAC authentication. If it is not, this is not applicable. Interview the SA to determine if all accounts not exempted by policy are using CAC authentication. If non-exempt accounts are not using CAC authentication, this is a finding.
Discussion
In accordance with CTO 07-015, PKI authentication is required. This provides stronger, two-factor authentication than using a username/password. NOTE: The following are exempt from this; however, they must meet all password requirements and must be documented with the IAO: - SIPRNET systems. - Stand-alone systems. - Application Accounts. - Students or unpaid employees (such as interns) who are not eligible to receive or not in receipt of a CAC, PIV, or ALT. - Warfighters and support personnel located at operational tactical locations conducting wartime operations that are not “collocated” with RAPIDS workstations to issue CAC, are not eligible for CAC, or do not have the capability to use ALT. - Test systems with an Interim Approval to Test (IATT) and provide protection via separate VPN, firewall, or security measures preventing access to network and system components from outside the protection boundary documented in the IATT.
Fix
Consult IBM documentation to determine the procedures necessary for configuring CAC authentication through PKI. Configure all accounts required by policy to use CAC authentication.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002760: The audit system must be configured to audit all administrative, privileged, and security actions.
Check the auditing configuration of the system. # more /etc/security/audit/events Verify the following events are configured. ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime, PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIDs, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv If any of these events are missing from the configuration, this is a finding. Check the ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime, PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIDs, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv audit events are defined in the audit classes' stanza 'classes:' of the /etc/security/audit/config file. #more /etc/security/audit/config Make note of the audit class(es) that the ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime, PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIDs, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv events are associated with. If the ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime, PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIDs, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv events are not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. #more /etc/security/audit/config If the class(es) that the ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime,PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIds, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv events are not associated with the default user and all the system users in the 'users:' stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Edit /etc/security/audit/events and add the following events to the list of audited events: ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime, PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIDs, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv. Edit /etc/security/audit/config and add the ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime, PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIDs, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv audit events to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes with the ACCT_Disable, ACCT_Enable, AUD_it, BACKUP_Export, DEV_Change, DEV_Configure, DEV_Create, FILE_Chpriv, FILE_Fchpriv, FILE_Mknod, FILE_Owner, FS_Chroot, FS_Mount, FS_Umount, PASSWORD_Check, PROC_Adjtime, PROC_Kill, PROC_Privilege, PROC_Setpgid, PROC_SetUserIDs, RESTORE_Import, TCBCK_Delete, USER_Change, USER_Create, USER_Reboot, USER_Remove, and USER_SetEnv events to the all users listed in the users: stanza.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002640: Default system accounts must be disabled or removed.
Determine if default system accounts (such as those for guest, sys, bin, uucp, nuucp, daemon, smtp, and lpd) have been disabled. Procedure: # lsuser -a account_locked ALL If there are any unlocked default system accounts, this is a finding.
Discussion
Vendor accounts and software may contain backdoors allowing unauthorized access to the system. These backdoors are common knowledge and present a threat to system security if the account is not disabled.
Fix
Lock the default system account(s). # chuser account_locked=true <user>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0090: The /etc/netsvc.conf file must be group-owned by bin, sys, or system.
Check the group ownership of the /etc/netcsvc.conf file. Procedure: # ls -lL /etc/netsvc.conf If the file is not group-owned by bin, sys, or system, this is a finding.
Discussion
The /etc/netsvc.conf file is used to specify the ordering of name resolution for the sendmail command, alias resolution for the sendmail command, and host name resolution routines. Malicious changes could prevent the system from functioning correctly or compromise system security.
Fix
Change the group owner of the /etc/netsvc.conf file to bin, sys, or system. Procedure: # chgrp system /etc/netsvc.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001730: All global initialization files must not have extended ACLs.
Check global initialization files for extended ACLs. Procedure: #aclget /etc/profile /etc/bashrc /etc/csh.login /etc/csh.cshrc /etc/environment /etc/.login /etc/security/environ /etc/security/.profile Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Global initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.
Fix
Remove the extended ACL from the global initialization file(s) and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006400: The Network Information System (NIS) protocol must not be used.
Perform the following to determine if NIS is active on the system. # ps -ef | egrep '(ypbind|ypserv)' If NIS is found active on the system, this is a finding.
Discussion
Due to numerous security vulnerabilities existing within NIS, it must not be used. Possible alternative directory services are NIS+ and LDAP.
Fix
Disable the use of NIS. Possible replacements are NIS+ and LDAP.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004620: The Sendmail server must have the debug feature disabled.
Check for an enabled debug command provided by the SMTP service. Procedure: # telnet localhost 25 debug If the command does not return a 500 error code of command unrecognized, this is a finding. If telnet is unavailable for testing, check the version of sendmail installed on the system. # echo \$Z | /usr/sbin/sendmail -bt -d0 If the sendmail reported version is less than 8.6, this is a finding.
Discussion
Debug mode is a feature present in older versions of Sendmail which, if not disabled, may allow an attacker to gain access to a system through the Sendmail service.
Fix
Obtain and install a more recent version of Sendmail, which does not implement the DEBUG feature.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN000253: The time synchronization configuration file (such as /etc/ntp.conf) must not have an extended ACL.
Check for an extended ACL on the NTP configuration file. # aclget /etc/ntp.conf If extended permissions are not disabled, this is a finding.
Discussion
A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. If an illicit time source is used for synchronization, the integrity of system logs and the security of the system could be compromised. If the configuration files controlling time synchronization are not protected, unauthorized modifications could result in the failure of time synchronization.
Fix
Remove the extended ACL from the ntp.conf file. #acledit /etc/ntp.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007820: The system must not have IP tunnels configured.
Determine if any IP tunnels are configured on the system. Check for IP tunnels. # lstun -a # ifconfig -a | grep -e gre -e gif -e cti -e sit If any tunnels are listed, this is a finding.
Discussion
IP tunneling mechanisms can be used to bypass network filtering.
Fix
Remove the configuration for any IP tunnels from the system. Remove tunnels listed with the lstun command. #rmtun -t <Tunnel id> -d Remove the tunneled IP interfaces. #ifconfig <if name> detach #rmdev -Rdl <if name>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006160: The /var/private/smbpasswd file must be owned by root.
Check the ownership of the smbpasswd file. # ls -l /var/private/smbpasswd If an smbpasswd file is not owned by root, this is a finding.
Discussion
If the smbpasswd file is not owned by root, the smbpasswd file may be maliciously accessed or modified, potentially resulting in the compromise of Samba accounts.
Fix
Change the owner of the smbpasswd file to root. # chown root /var/private/smbpasswd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008440: Automated file system mounting tools must not be enabled unless needed.
Determine if the system uses automated file system mounting tools (such as autofs or automount). AIX can use automount facility. #ps -ef | grep -v grep | grep automount If the automount process is running, this is a finding.
Discussion
Automated file system mounting tools may provide unprivileged users with the ability to access local media and network shares. If this access is not necessary for the system’s operation, it must be disabled to reduce the risk of unauthorized access to these resources.
Fix
Disable the automated file system mounting tools. Empty the /etc/auto_master file kill automount kill < pid of automount >
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN008180: If the system is using LDAP for authentication or account information, the TLS certificate authority file and/or directory (as appropriate) must have mode 0644 (0755 for directories) or less permissive.
Determine the SSL certificate key database file and/or directory. Procedure: # grep -i '^ldapsslkeyf' /etc/security/ldap/ldap.cfg For each file or directory returned, check the permissions. Procedure: # ls -lLd <certpath> If the mode of the file is more permissive than 0644 (or 0755 for directories), this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Change the mode of the file to 0644 or the directory to 0755 or less permissive. File Procedure: # chmod 0644 < SSL key database certpath > Directory Procedure: # chmod 0755 < SSL key database certpath >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009280: The system must not have the PCNFS service active.
Check the /etc/inetd.conf file for active PCNFS service. #grep pcnfsd /etc/inetd.conf | grep -v \# If the PCNFS service is enabled, this is a finding.
Discussion
The PCNFS service predates Microsoft’s SMB specifications. If a similar service is needed to share files from a Windows based OS to a UNIX based OS, consider SAMBA.
Fix
Edit /etc/inetd.conf and comment out the PCNFS service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001845: Global initialization files' library search paths must contain only absolute paths.
Check the global initialization files' library search paths. #egrep '(LD_LIBRARY_PATH|LIBPATH)' /etc/profile /etc/bashrc /etc/security/.login /etc/environment /etc/security/environ The LIBPATH or LD_LIBRARY_PATH variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a relative path, and this is a finding.
Discussion
The library search path environment variable(s) contain a list of directories for the dynamic linker to search to find libraries. If this path includes the current working directory or other relative paths, libraries in these directories may be loaded instead of system libraries. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.
Fix
Edit the global initialization files /etc/profile /etc/bashrc /etc/security/.login /etc/environment /etc/security/environ and remove relative entries from the library search path variables. #vi /etc/profile /etc/bashrc /etc/security/.login /etc/environment /etc/security/environ
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005506: The SSH daemon must be configured to not use Cipher-Block Chaining (CBC) ciphers.
Check the SSH daemon configuration for allowed ciphers. # grep -i ciphers /etc/ssh/sshd_config | grep -v '^#' If no lines are returned, or the returned ciphers list contains any cipher ending with cbc, this is a finding.
Discussion
The Cipher-Block Chaining (CBC) mode of encryption as implemented in the SSHv2 protocol is vulnerable to chosen plain text attacks and must not be used.
Fix
Edit /etc/ssh/sshd_config and add or edit the "Ciphers" line. Only include ciphers that start with "3des" or "aes" and do not contain "cbc". For the list of available ciphers for the particular version of your software, consult the sshd_config manpage. Restart the SSH daemon.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003611: The system must log martian packets.
Determine if the system is configured to log martian packets. Examine the IPF rules on the system. # lsfilt -a There must be rules to log inbound traffic containing invalid source addresses, which minimally include the system's own addresses and broadcast addresses for attached subnets. If no such rules exist, this is a finding.
Discussion
Martian packets are packets containing addresses known by the system to be invalid. Logging these messages allows the SA to identify misconfigurations or attacks in progress.
Fix
Configure the system to log martian packets. Add rules to log inbound traffic containing invalid source addresses, which minimally include the system's own addresses and broadcast addresses for attached subnets. For example, consider a system with a single network connection having IP address 192.168.1.10 with a local subnet broadcast address of 192.168.1.255. Packets with source addresses of 192.168.1.10 and 192.168.1.255 must be logged if received by the system from the network connection. Use the smit utility or genfilt command to add logging of martian packets (packets with a source address of 192.168.1.10 and 192.168.1.255). # smitty ipsec4 OR # genfilt -v4 -a P -s 192.168.1.10 -m 0.0.0.0 -d 0.0.0.0 -M -0.0.0.0 -c all -o any -O any -p 0 -P 0 -w I -l y -i en0 # genfilt -v4 -a P -s 192.168.1.255 -m 0.0.0.0 -d 0.0.0.0 -M -0.0.0.0 -c all -o any -O any -p 0 -P 0 -w I -l y -i en0
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000595: The password hashes stored on the system must have been generated using a FIPS 140-2 approved cryptographic hashing algorithm.
Verify no password hashes in /etc/passwd. # cat /etc/passwd | cut -f2,2 -d":" If there are password hashes present, this is a finding. Verify all password hashes in /etc/security/passwd begin with {ssha256} or {ssha512}. Procedure: # cat /etc/passwd | cut -f2,2 -d ":" # cat /etc/security/passwd | grep password If any password hashes are present not beginning with {ssha256} or {ssha512}, this is a finding.
Discussion
Systems must employ cryptographic hashes for passwords using the SHA-2 family of algorithms or FIPS 140-2 approved successors. The use of unapproved algorithms may result in weak password hashes that are more vulnerable to compromise.
Fix
Change the passwords for all accounts using non-compliant password hashes. # passwd account OR # smitty passwd (This requires that GEN000590 is already met.)
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004220: Administrative accounts must not run a web browser, except as needed for local service administration.
Look in the root account home directory for a .netscape or a .mozilla directory. If none exists, this is not a finding. If there is one, verify with the root users and the IAO what the intent of the browsing is. Some evidence may be obtained by using the browser to view cached pages under the .netscape directory.
Discussion
If a web browser flaw is exploited while running as a privileged user, the entire system could be compromised. Specific exceptions for local service administration should be documented in site-defined policy. These exceptions may include HTTP(S)-based tools used for the administration of the local system, services, or attached devices. Examples of possible exceptions are HP’s System Management Homepage (SMH), the CUPS administrative interface, and Sun's StorageTek Common Array Manager (CAM) when these services are running on the local system.
Fix
Enforce policy requiring administrative accounts use web browsers only for local service administration.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN006225: Samba must be configured to use an authentication mechanism other than share.
Check the security mode of the Samba configuration. # grep -i security /usr/lib/smb.conf If the security mode is share, this is a finding.
Discussion
Samba share authentication does not provide for individual user identification and must not be used.
Fix
Edit the /usr/lib/smb.conf file and change the security setting to user or another valid setting other than share. # vi /usr/lib/smb.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001810: Skeleton files must not have extended ACLs.
Check skeleton files for extended ACLs. Procedure: #aclget /etc/security/.profile #aclget /etc/security/mkuser.sys Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
If the skeleton files are not protected, unauthorized personnel could change user startup parameters and possibly jeopardize user files.
Fix
Remove the extended ACL from the skeleton file(s) and disable extended permissions. #acledit /etc/security/.profile #acledit /etc/security/mkuser.sys
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004560: The SMTP service's SMTP greeting must not provide version information.
Check for the Sendmail version being displayed in the greeting. # telnet localhost 25 If a version number is displayed, this is a finding.
Discussion
The version of the SMTP service can be used by attackers to plan an attack based on vulnerabilities present in the specific version.
Fix
Ensure Sendmail or its equivalent has been configured to mask the version information. If necessary, change the O SmtpGreetingMessage line in the /etc/sendmail.cf file. O SmtpGreetingMessage=$j Sendmail $v/$Z; $b Change it to: O SmtpGreetingMessage= Mail Server Ready ; $b
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001361: NIS/NIS+/yp command files must not have extended ACLs.
Determine if any NIS/NIS+/yp command files have an extended ACL. Check if extended permissions are disabled. Procedure: # aclget /var/nis # aclget /var/yp If extended permissions are not disabled, this is a finding.
Discussion
NIS/NIS+/yp files are part of the system's identification and authentication processes and are, therefore, critical to system security. ACLs on these files could result in unauthorized modification, which could compromise these processes and the system.
Fix
Remove the extended ACL from the NS/NIS+/yp command file(s) and disable extended permissions. #acledit < directory >/< file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000680: The system must require passwords to contain no more than three consecutive repeating characters.
Check the maxrepeats setting. Procedure: # grep -i maxrepeats /etc/security/user OR # lsuser -a maxrepeats ALL If the maxrepeats setting is greater than 3, this is a finding.
Discussion
To enforce the use of complex passwords, the number of consecutive repeating characters is limited. Passwords with excessive repeated characters may be more vulnerable to password-guessing attacks.
Fix
Use the chsec command to set maxrepeats to 3. # chsec -f /etc/security/user -s default -a maxrepeats=3 # chuser maxrepeats=3 < user id >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006210: The /var/private/smbpasswd file must not have an extended ACL.
Check the group ownership of the Samba configuration file. # aclget /var/private/smbpasswd If the extended attributes are not disabled, this is a finding.
Discussion
If the permissions of the smbpasswd file are too permissive, the smbpasswd file may be maliciously accessed or modified, potentially resulting in the compromise of Samba accounts.
Fix
Remove the extended ACL from the /var/private/smbpasswd file. # acledit /var/private/smbpasswd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002460: The system must be checked weekly for unauthorized setgid files, as well as, unauthorized modification to authorized setgid files.
Determine if a weekly automated or manual process is used to generate a list of setgid files on the system and compare it with the prior list. If no such process is in place, this is a finding.
Discussion
Files with the setgid bit set will allow anyone running these files to be temporarily assigned the group id of the file. While many system files depend on these attributes for proper operation, security problems can result if setgid is assigned to programs that allow reading and writing of files, or shell escapes.
Fix
Establish a weekly automated or manual process to generate a list of setgid files on the system and compare it with the prior list. To create a list of setgid files use the following command. # find / -perm -2000 > setgid-file-list
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003120: Cron and crontab directories must be owned by root or bin.
Check the owner of the crontab directory. # ls -ld /var/spool/cron/crontabs If the owner of the crontab directory is not root or bin, this is a finding.
Discussion
Incorrect ownership of the cron or crontab directories could permit unauthorized users the ability to alter cron jobs and run automated jobs as privileged users. Failure to give ownership of cron or crontab directories to root or to bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the owner of the crontab directory. # chown root /var/spool/cron/crontabs
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005505: The SSH daemon must be configured to only use FIPS 140-2 approved ciphers.
Check the SSH daemon configuration for allowed ciphers. # grep -i ciphers /etc/ssh/sshd_config | grep -v '^#' If no lines are returned, or the returned ciphers list contains any cipher not starting with 3des or aes, this is a finding.
Discussion
DoD information systems are required to use FIPS 140-2 approved ciphers. SSHv2 ciphers meeting this requirement are 3DES and AES.
Fix
Edit /etc/ssh/sshd_config and add or edit the "Ciphers" line. Only include ciphers that start with "3des" or "aes" and do not contain "cbc". For the list of available ciphers for the particular version of your software, consult the sshd_config manpage. Restart the SSH daemon.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001570: All files and directories contained in user home directories must not have extended ACLs.
Check the contents of user home directories for files with extended ACLs. Procedure: # cat /etc/passwd | cut -f 6,6 -d ":" | xargs -n1 -IDIR aclget DIR OR #aclget <directory>/<file> Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Excessive permissions allow unauthorized access to user files.
Fix
Remove the extended ACL(s) from the files and directories in user home directories and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002430: Removable media, remote file systems, and any file system not containing approved device files must be mounted with the nodev option.
If the system does not support a nodev option, this is not applicable. Check /etc/filesystems and verify the nodev mount option (options = ) is used on any file systems mounted from removable media or network shares, or file systems not containing any approved device files. If any such file system is not using the nodev option, this is a finding.
Discussion
The nodev (or equivalent) mount option causes the system to not handle device files as system devices. This option must be used for mounting any file system not containing approved device files. Device files can provide direct access to system hardware and can compromise security if not protected.
Fix
Edit /etc/filesystems and add the options = nodev to all entries for remote or removable media file systems, and file systems containing no approved device files.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003930: The hosts.lpd (or equivalent) file must be group-owned by bin, sys, or system.
Check the group ownership of the /etc/hosts.lpd file. Procedure: # ls -lL /etc/hosts.lpd If the file is not group owned by bin, sys, or system, this is a finding.
Discussion
Failure to give group ownership of the hosts.lpd file to bin, sys, or system provides the members of the owning group and possible unauthorized users, with the potential to modify the hosts.lpd file. Unauthorized modifications could disrupt access to local printers from authorized remote hosts or permit unauthorized remote access to local printers.
Fix
Change the group owner of the hosts.lpd file. Procedure: # chgrp sys /etc/hosts.lpd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005536: The SSH daemon must perform strict mode checking of home directory configuration files.
Check the SSH daemon configuration for the StrictModes setting. # grep -i StrictModes /etc/ssh/sshd_config | grep -v '^#' If the setting is present and set to "no", this is a finding. If the setting is not present or is set to "yes", this is not a finding.
Discussion
If other users have access to modify user-specific SSH configuration files, they may be able to log into the system as another user.
Fix
Edit the /etc/sshd/sshd_config file and remove the StrictModes setting or change the value of the StrictModes setting to "yes".
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002825: The audit system must be configured to audit the loading and unloading of dynamic kernel modules.
Determine if the system is configured to audit the loading and unloading of dynamic kernel modules. Check the system's audit configuration. # more /etc/security/audit/events Confirm the following events are configured: DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure, and DEV_Remove. If any of these events are not configured, this is a finding. Check the File DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure, and DEV_Remove. Audit events are defined in the audit classes stanza classes: of the /etc/security/audit/config file. #more /etc/security/audit/config Make note of the audit class(es) the DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure, and DEV_Remove events are associated with. If the DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure, and DEV_Remove events are not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. #more /etc/security/audit/config If the class(es) that the DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure, and DEV_Remove events are not associated with the default user and all the system users in the users: stanza, this is a finding.
Discussion
Actions concerning dynamic kernel modules must be recorded as they are substantial events. Dynamic kernel modules can increase the attack surface of a system. A malicious kernel module can be used to substantially alter the functioning of a system, often with the purpose of hiding a compromise from the SA.
Fix
Configure the system to audit the loading and unloading of dynamic kernel modules. Edit /etc/security/audit/events and add the DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure, and DEV_Remove events to the list of audited events. Edit /etc/security/audit/config and add the DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure, and DEV_Remove audit events to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes that has the DEV_Create, FILE_Mknod, DEV_Configure, DEV_Stop, DEV_Unconfigure and DEV_Remove events to the all users listed in the 'users:' stanza.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005340: Management Information Base (MIB) files must have mode 0640 or less permissive.
Check the modes for all Management Information Base (MIB) files on the system. Procedure: # find / -name *.mib -print # ls -lL <mib file> If any file is returned that does not have mode 0640 or less permissive, this is a finding.
Discussion
The ability to read the MIB file could impart special knowledge to an intruder or malicious user about the ability to extract compromising information about the system or network.
Fix
Change the mode of MIB files to 0640. Procedure: # chmod 0640 <mib file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006000: The system must not have a public Instant Messaging (IM) client installed.
If an IM client is installed, ask the SA if it has access to any public domain IM servers. If it does have access to public servers, this is a finding.
Discussion
Public Instant Messaging (IM) systems are not approved for use and may result in the unauthorized distribution of information. IM clients provide a way for a user to send a message to one or more other users in real time. Additional capabilities may include file transfer and support for distributed game playing. Communication between clients and associated directory services are managed through messaging servers. Commercial IM clients include AOL Instant Messenger (AIM), MSN Messenger, and Yahoo! Messenger. IM clients present a security issue when the clients route messages through public servers. The obvious implication is potentially sensitive information could be intercepted or altered in the course of transmission. This same issue is associated with the use of public email servers. In order to reduce the potential for disclosure of sensitive Government information and to ensure the validity of official government information, IM clients connecting to public IM services will not be installed. Clients used to access internal or DoD-controlled IM services are permitted.
Fix
Uninstall the IM client from the system, or configure the client to only connect to DoD-approved IM services.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0340: The /etc/ftpaccess.ctl file must have mode 0640 or less permissive.
Check the permissions of the /etc/ftpaccess.ctl file. # ls -l /etc/ftpaccess.ctl If the ftpaccess.ctl file has a mode more permissive than 0640, this is a finding.
Discussion
Excessive permissions on the ftpaccess.ctl file could permit unauthorized modification. Unauthorized modification could result in Denial of Service to authorized FTP users or permit unauthorized access to system information.
Fix
Change the mode of the /etc/ftpaccess.ctl file to 0640. # chmod 0640 /etc/ftpaccess.ctl
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004430: Files executed through a mail aliases file must not have extended ACLs.
Examine the contents of the /etc/mail/aliases file. For each file referenced, check the permissions of the file. #aclget [File referenced from alias] Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Excessive permissions on files executed through a mail alias file could result in modification by an unauthorized user, execution of malicious code, and/or system compromise.
Fix
Remove the extended ACL from the file(s) referenced from the aliases file and disable extended permissions. #acledit [File referenced from aliases]
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001830: All skeleton files (typically in /etc/skel) must be group-owned by security.
Verify the skeleton files are group-owned by security. Procedure: # ls -alL /etc/security/.profile /etc/security/mkuser.sys If a skeleton file is not group-owned by security, this is a finding.
Discussion
If the skeleton files are not protected, unauthorized personnel could change user start-up parameters and possibly jeopardize user files.
Fix
Change the group owner of the skeleton file to security. Procedure: # chgrp security /etc/security/.profile /etc/security/mkuser.sys
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000400: The Department of Defense (DoD) login banner must be displayed immediately prior to, or as part of, console login prompts.
Access the system console and make a logon attempt. Check for either of the following login banners based on the character limitations imposed by the system. An exact match is required. If one of these banners is not displayed, this is a finding. "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details. " OR "I've read & consent to terms in IS user agreem't."
Discussion
Failure to display the login banner prior to a logon attempt will negate legal proceedings resulting from unauthorized access to system resources.
Fix
Edit /etc/security/login.cfg and assign the herald value for the default and /dev/console stanzas to one of the DoD login banners (based on the character limitations imposed by the system). # chsec -f /etc/security/login.cfg -s default -a herald="<DoD Login Banner>" OR # vi /etc/security/login.cfg and add a herald = <DoD Login Banner> statement to the default stanza DoD Login Banners: "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details. " OR "I've read & consent to terms in IS user agreem't."
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002220: All shell files must have mode 0755 or less permissive.
Obtain a list of system shells from /etc/security/login.cfg and check the permissions of these shells. Procedure: #grep shells /etc/security/login.cfg | grep -v \* | cut -f 2 -d = | sed s/,/\ /g | xargs -n1 ls -l If any shell has a mode more permissive than 0755, this is a finding. Obtain a list of system shells from /etc/shells and check the ownership of these shells. Procedure: #cat /etc/shells | xargs -n1 ls -l If any shell has a mode more permissive than 0755, this is a finding.
Discussion
Shells with world/group write permissions give the ability to maliciously modify the shell to obtain unauthorized access.
Fix
Change the mode of the shell. # chmod 0755 < shell >
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN006200: The /var/private/smbpasswd file must have mode 0600 or less permissive.
Check smbpasswd mode. Procedure: # ls -lL /var/private/smbpasswd If smbpasswd has a mode more permissive than 0600, this is a finding.
Discussion
If the smbpasswd file has a mode more permissive than 0600, the smbpasswd file may be maliciously accessed or modified, potentially resulting in the compromise of Samba accounts.
Fix
Change the mode of the smbpasswd file to 0600. Procedure: # chmod 0600 /var/private/smbpasswd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003720: The inetd.conf file, xinetd.conf file, and the xinetd.d directory must be owned by root or bin.
Check the ownership of inetd.conf file. Procedure: # ls -lL /etc/inetd.conf This is a finding if any of the above files or directories are not owned by root or bin.
Discussion
Failure to give ownership of sensitive files or utilities to root provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the ownership of the inetd.conf file to root or bin. Procedure: # chown root /etc/inetd.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004900: The ftpusers file must contain account names not allowed to use FTP.
Check the contents of the ftpusers file. If the system has accounts not allowed to use FTP and are not listed in the ftpusers file, this is a finding. # more /etc/ftpusers
Discussion
The ftpusers file contains a list of accounts not allowed to use FTP to transfer files. If the file does not contain the names of all accounts not authorized to use FTP, then unauthorized use of FTP may take place.
Fix
Add accounts not allowed to use FTP to the /etc/ftpusers file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005525: The SSH client must not permit GSSAPI authentication unless needed.
Check the SSH clients configuration for the GSSAPI authentication setting. # grep -i GSSAPIAuthentication /etc/ssh/ssh_config | grep -v '^#' If the setting is present and set to "yes", this is a finding. If the setting is absent or set to "no", this is not a finding.
Discussion
GSSAPI authentication is used to provide additional authentication mechanisms to applications. Allowing GSSAPI authentication through SSH exposes the system’s GSSAPI to remote hosts, increasing the attack surface of the system. GSSAPI authentication must be disabled unless needed.
Fix
Edit the /etc/ssh/ssh_config file and remove the GSSAPIAuthentication setting or change the GSSAPIAuthentication setting to "no".
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000740: All non-interactive/automated processing account passwords must be changed at least once per year or be locked.
NOTE: This will always require a manual review. This is a local policy issue/question. Ask the SA if there are any automated processing accounts on the system. If there are automated processing accounts on the system, ask the SA if the passwords for those automated accounts are changed at least once a year. If the SA indicates passwords for automated processing accounts are not changed once per year, this is a finding. Procedure: Go to last password change date for the system account. # grep -p <account_name> /etc/security/passwd | grep lastupdate To examine the time a password was last changed, the following perl script has been provided. Put the lastupdate value in the <lastupdate>. #perl -e 'use POSIX; print strftime("%c\n" , localtime(<lastupdate>));'
Discussion
Limiting the lifespan of authenticators limits the period of time an unauthorized user has access to the system while using compromised credentials and reduces the period of time available for password-guessing attacks to run against a single password. Locking the password for non-interactive and automated processing accounts is preferred as it removes the possibility of accessing the account by a password. On some systems, locking the passwords of these accounts may prevent the account from functioning properly. Passwords for non-interactive/automated processing accounts must not be used for direct logon to the system.
Fix
Implement or establish procedures to change the passwords of automated processing accounts at least once per year. #passwd account
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002716: System audit tool executables must be group-owned by bin, sys, or system.
Determine the group ownership of system audit tool executables. Audit tools include, but are not limited to, audit, auditcat, auditconv, auditpr, auditselect, auditstream, auditbin, and auditmerge. Procedure: # ls -lL `which <audit tool executable>` If any system audit tool executable is not group-owned by bin, sys, or system, this is a finding.
Discussion
To prevent unauthorized access or manipulation of system audit logs, the tools for manipulating those logs must be protected.
Fix
Change the group owner of system audit tool executables to root, bin, sys, or system. Procedure: # chgrp system < system audit tool executable>
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001394: The /etc/group file must not have an extended ACL.
Verify the /etc/group file has no extended ACL. Procedure: #aclget /etc/group Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
The /etc/group file is critical to system security and must be protected from unauthorized modification. The group file contains a list of system groups and associated information.
Fix
Remove the extended ACL from the /etc/group file and disable extended permissions. #acledit /etc/group
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001480: All users' home directories must have mode 0750 or less permissive.
Check the home directory mode of each user in /etc/passwd. Procedure: # cut -d : -f 6 /etc/passwd | xargs -n1 ls -ld | more If a user's home directory's mode is more permissive than 0750, this is a finding. NOTE: Application directories are allowed and may need 0755 permissions (or greater) for correct operation.
Discussion
Excessive permissions on home directories allow unauthorized access to user's files.
Fix
Change the mode of users' home directories to 0750 or less permissive. Procedure (example): # chmod 0750 <home directory>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008680: If the system boots from removable media, it must be stored in a safe or similarly secured container.
Ask the SA if the system boots from removable media. If so, ask if the boot media is stored in a secure container when not in use. If it is not, this is a finding.
Discussion
Storing the boot loader on removable media in an insecure location could allow a malicious user to modify the systems boot instructions or boot to an insecure operating system.
Fix
Store the system boot media in a secure container when not in use.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN009300: The inetd time service must not be active on the system on the inetd daemon.
Check the /etc/inetd.conf file for TCP and UDP time service. grep time /etc/inetd.conf | grep -v daytime | grep -v \# If the time service is enabled, this is a finding.
Discussion
The time service is an internal inetd function is used by the rdate command. This service is sometimes used to synchronize clocks at boot time. The service is outdated. Use the ntpdate command instead.
Fix
Edit the /etc/inetd.conf file and comment out the time service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007700: The IPv6 protocol handler must not be bound to the network stack unless needed.
AIX comes with IPv6 protocol handler installed and active. The only configured IPv6 address is the loopback localhost adapter. Check if any other interfaces have IPv6 addresses active. # ifconfig -a If any IPv6 addresses are configured on any network interfaces other than loopback and IPv6 is not needed, this is a finding.
Discussion
IPv6 is the next version of the Internet protocol. Binding this protocol to the network stack increases the attack surface of the host.
Fix
Unbind the IPv6 protocol handler from the network stack. Edit /etc/rc.tcpip and comment out autoconf6 to prevent IPv6 from auto starting. Unconfigure IPv6 addresses from interfaces not used with smit. #smit chinet6
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005760: The NFS export configuration file must have mode 0644 or less permissive.
# ls -lL /etc/exports If the file has a mode more permissive than 0644, this is a finding.
Discussion
Excessive permissions on the NFS export configuration file could allow unauthorized modification of the file, which could result in Denial of Service to authorized NFS exports and the creation of additional unauthorized exports.
Fix
# chmod 0644 /etc/exports
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN006580: The system must use an access control program.
Determine if TCP_WRAPPERS is being used. # grep tcpd /etc/inetd.conf If no services are listed, this is a finding.
Discussion
Access control programs (such as TCP_WRAPPERS) provide the ability to enhance system security posture.
Fix
Edit /etc/inetd.conf and use tcpd to wrap services. Use SMIT to install TCP Wrappers from the AIX Expansion pack media as fileset netsec.options.tcpwrappers.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005360: The snmpd.conf file must be owned by root.
Determine the owner of the SNMP configuration file. Consult vendor documentation to determine the location and name of the file. Procedure: # find / -name "snmpd*.conf" # ls -lL <snmpd.conf> If the snmpd.conf file is not owned by root, this is a finding.
Discussion
The snmpd.conf file contains authenticators and must be protected from unauthorized access and modification. If the file is not owned by root, it may be subject to access and modification from unauthorized users.
Fix
Change the owner of the snmpd.conf file to bin. Procedure: # chown bin <snmpd.conf file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001460: All interactive user home directories defined in the /etc/passwd file must exist.
Use pwck to check that assigned home directories exist. Procedure: # usrck -n ALL If any user's assigned home directory does not exist, this is a finding.
Discussion
If a user has a home directory defined that does not exist, the user may be given the / directory, by default, as the current working directory upon logon. This could create a Denial of Service because the user would not be able to perform useful tasks in this location.
Fix
If a user has no home directory, determine why. If possible, delete accounts with no home directory. If the account is valid, then create the home directory using the appropriate system administration utility or manually create, i.e., mkdir <directory name>; copy the skeleton files into the directory; chown <user name> <directory name> for the new directory and the skeleton files. Document all changes.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003060: Default system accounts (with the exception of root) must not be listed in the cron.allow file or must be included in the cron.deny file, if cron.allow does not exist.
Check the cron.allow and cron.deny files for the system. # more /var/adm/cron/cron.allow # more /var/adm/cron/cron.deny If a default system account (such as bin, sys, adm, or others) is listed in the cron.allow file, or not listed in the cron.deny file if no cron.allow file exists, this is a finding.
Discussion
To centralize the management of privileged account crontabs, of the default system accounts, only root may have a crontab.
Fix
Remove default system accounts (such as bin, sys, adm, or others) from the cron.allow file if it exists, or add those accounts to the cron.deny file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005590: The system must not be running any routing protocol daemons, unless the system is a router.
Check for any running routing protocol daemons. # ps -ef | egrep '(ospf|route|bgp|zebra|quagga|gate)' If any routing protocol daemons are listed, this is a finding.
Discussion
Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network.
Fix
Disable any routing protocol daemons.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004400: Files executed through a mail aliases file must be owned by root and must reside within a directory owned and writable only by root.
Find the aliases file on the system. Procedure: # find / -name aliases -depth -print # more < aliases file location > Examine the aliases file for any directories or paths that may be utilized. Procedure: # ls -lL < path > Check if the file or parent directory is owned by root. If not, this is a finding.
Discussion
If a file executed through a mail aliases file is not owned and writable only by root, it may be subject to unauthorized modification. Unauthorized modification of files executed through aliases may allow unauthorized users to attain root privileges.
Fix
Edit the /etc/mail/aliases file (alternatively, /usr/lib/sendmail.cf). Locate the entries executing a program. They will appear similar to the following line. Aliasname: : /usr/local/bin/ls (or some other program name) Ensure root owns the programs and the directory(ies) they reside in by using the chown command to change owner to root. Procedure: # chown root filename
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN003920: The hosts.lpd (or equivalent) file must be owned by root, bin, sys, or lp.
Locate any print service configuration file on the system. Consult vendor documentation to verify the names and locations of print service configuration files on the system. Procedure: # find /etc -name hosts.lpd -print # find /etc -name Systems -print If no print service configuration file is found, this is not applicable. Check the ownership of the print service configuration file(s). Procedure: # ls -lL <print service file> If the owner of the file is not root, sys, bin, or lp, this is a finding.
Discussion
Failure to give ownership of the hosts.lpd file to root, bin, sys, or lp provides the designated owner, and possible unauthorized users, with the potential to modify the hosts.lpd file. Unauthorized modifications could disrupt access to local printers from authorized remote hosts or permit unauthorized remote access to local printers.
Fix
Change the owner of the /etc/hosts.lpd file (or equivalent, such as /etc/lp/Systems) to root, lp, or another privileged UID. Consult vendor documentation to determine the name and location of print service configuration files. Procedure: # chown root /etc/hosts.lpd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004680: The SMTP service must not have the VRFY feature active.
Determine if VRFY is disabled. Procedure: # telnet localhost 25 vrfy root If the command does not return a 500 error code of command unrecognized, this is a finding. OR Locate the sendmail.cf configuration file. Procedure: # find / -name sendmail.cf -print # grep -v "^#" |grep -i vrfy Ensure the VRFY command is disabled with an entry in the sendmail.cf file. The entry could be any one of Opnovrfy, novrfy, or goaway, which could also have other options included, such as noexpn. The goaway argument encompasses many things, such as novrfy and noexpn. If no setting to disable VRFY is found, this is a finding.
Discussion
The VRFY (Verify) command allows an attacker to determine if an account exists on a system, providing significant assistance to a brute force attack on user accounts. VRFY may provide additional information about users on the system, such as the full names of account owners.
Fix
If you are running Sendmail, add the line Opnovrfy to your Sendmail configuration file, usually located in /etc/sendmail.cf. For other mail servers, contact the vendor for information on how to disable the verify command. Newer versions of Sendmail are available at http://www.sendmail.org or from ftp://ftp.cs.berkeley.edu/ucb/sendmail.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000000-AIX0230: The system must provide protection against IP fragmentation attacks.
Check the value of the ip_nfrag parameter. # /usr/sbin/no -o ip_nfrag If the result returned is less than 200, this is a finding.
Discussion
The parameter ip_nfrag provides an additional layer of protection against IP fragmentation attacks. The value the ip_nfrag specifies is the maximum number of fragments of an IP packet that can be kept in the IP reassembly queue at any time. The default value of this network option is 200. This is a reasonable value for most environments and offers protection from IP fragmentation attacks.
Fix
Set the ip_nfrag parameter to 200. # /usr/sbin/no -p -o ip_nfrag=200
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001540: All files and directories contained in interactive user's home directories must be owned by the home directory's owner.
For each user in the /etc/passwd file, check for the presence of files and directories within the user's home directory not owned by the home directory owner. Procedure: # find /<usershomedirectory> ! -fstype nfs ! -user <username> ! \( -name .login -o -name .cshrc -o -name .logout -o -name .profile -o -name .bash_profile -o -name .bashrc -o -name .env -o -name .dtprofile -o -name .dispatch -o -name .emacs -o -name .exrc \) -exec ls -ld {} \; If user's home directories contain files or directories not owned by the home directory owner, this is a finding.
Discussion
If users do not own the files in their directories, unauthorized users may be able to access them. Additionally, if files are not owned by the user, this could be an indication of system compromise.
Fix
Change the ownership of files and directories in user's home directories to the owner of the home directory. Procedure: # chown accountowner filename OR # find /<usershomedirectory> ! -fstype nfs ! -user <username> ! /( -name .login -o -name .cshrc -o -name .logout -o -name .profile -o -name .bash_profile -o -name .bashrc -o -name .env -o -name .dtprofile -o -name .dispatch -o -name .emacs -o -name .exrc \) -exec chown <username> {} \;
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001605: Run control scripts' library search paths must contain only absolute paths.
Verify run control scripts' library search paths. Procedure: # grep -r LIBPATH /etc/rc* The variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a relative path, and this is a finding.
Discussion
The library search path environment variable(s) contains a list of directories for the dynamic linker to search to find libraries. If this path includes the current working directory or other relative paths, libraries in these directories may be loaded instead of system libraries. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.
Fix
Edit run control scripts' library search path variables. Remove empty entries or entries that are not absolute paths.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000340: UIDs reserved for system accounts must not be assigned to non-system accounts.
Check the UID assignments of all accounts. # more /etc/passwd Confirm all accounts with a UID of 128 and below are used by a system account. If a UID reserved for system accounts (0-128) is used by a non-system account, this is a finding.
Discussion
Reserved UIDs are typically used by system software packages. If non-system accounts have UIDs in this range, they may conflict with system software, possibly leading to the user having permissions to modify system files.
Fix
Using the usermod command, change the UID numbers for non-system accounts with reserved UIDs (those less or equal to 128). # usermod -u <uid> login Alternatively, smit can be used for this same purpose. #smitty users
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004410: Files executed through a mail aliases file must be group-owned by root, bin, sys, or other, and must reside within a directory group-owned by root, bin, sys, or other.
Examine the contents of the /etc/mail/aliases file. # cat /etc/mail/aliases | cut -f 2,2 -d ":" | grep "|" For each file referenced, check the group ownership of the file. # ls -lL <file referenced from aliases> If the group owner of any file is not root, bin, sys or other, this is a finding.
Discussion
If a file executed through a mail aliases file is not group-owned by root or a system group, it may be subject to unauthorized modification. Unauthorized modification of files executed through aliases may allow unauthorized users to attain root privileges.
Fix
Change the group ownership of the file referenced from /etc/mail/aliases. # chgrp root <file referenced from aliases>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004540: The SMTP service HELP command must not be enabled.
Check to see if help is disabled in Sendmail. Procedure: # telnet <host> 25 help If the help command returns any Sendmail version information, this is a finding.
Discussion
The HELP command should be disabled to mask version information. The version of the SMTP service software could be used by attackers to target vulnerabilities present in specific software versions.
Fix
To disable the SMTP HELP command create an empty Sendmail help file. # > /etc/mail/help
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003865: Network analysis tools must not be installed.
Determine if any network analysis tools are installed. Procedure: # find / -name ethereal # find / -name wireshark # find / -name tshark # find / -name netcat # find / -name tcpdump # find / -name snoop If any network analysis tools are found, this is a finding. Additional Information: The binary tcpdump is provided in the bos.net.tcp.server fileset and this fileset cannot be uninstalled.
Discussion
Network analysis tools allow for the capture of network traffic visible to the system.
Fix
Remove the network analysis tool binary from the system. Procedure: # rm /usr/sbin/tcpdump
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002700: System audit logs must have mode 0640 or less permissive.
Perform the following to determine the location of audit logs and then check the mode of the files. Procedure: # grep -p bin: /etc/security/audit/config Directories to search will be listed under the bin stanza. # ls -la <audit directories> If any audit log file has a mode more permissive than 0640, this is a finding.
Discussion
If a user can write to the audit logs, audit trails can be modified or destroyed and system intrusion may not be detected. System audit logs are those files generated from the audit system and do not include activity, error, or other log files created by application software.
Fix
Change the mode of the audit log directories/files. # chmod 0750 <audit directory> # chmod 0640 <audit file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004000: The traceroute file must have mode 0700 or less permissive.
# ls -lL /usr/bin/traceroute If the traceroute command has a mode more permissive than 0700, this is a finding.
Discussion
If the mode of the traceroute executable is more permissive than 0700, malicious code could be inserted by an attacker and triggered whenever the traceroute command is executed by authorized users. Additionally, if an unauthorized user is granted executable permissions to the traceroute command, it could be used to gain information about the network topology behind the firewall. This information may allow an attacker to determine trusted routers and other network information possibly leading to system and network compromise.
Fix
Change the mode of the traceroute command. # chmod 0700 /usr/bin/traceroute
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005810: All NFS-exported system files and system directories must be group-owned by root, bin, sys, or system.
Determine if the NFS exported directories on the system are group-owned by root. If any are not, this is a finding.
Discussion
Failure to give group ownership of sensitive files or directories to root provides the members of the owning group with the potential to access sensitive information or change system configuration which could weaken the system's security posture.
Fix
Change the group owner of NFS exported directories to root.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002440: The owner, group owner, mode, ACL, and location of files with the setgid bit set must be documented using site-defined procedures.
Locate all setgid files on the system. Procedure: # find / -perm -2000 If the ownership, permissions, location, and ACLs of all files with the setgid bit set are not documented, this is a finding.
Discussion
All files with the setgid bit set will allow anyone running these files to be temporarily assigned the GID of the file. While many system files depend on these attributes for proper operation, security problems can result if setgid is assigned to programs that allow reading and writing of files, or shell escapes.
Fix
All files with the sgid bit set will be documented in the system baseline and authorized by the Information Systems Security Officer. Locate all sgid files with the following command: #find / -perm -2000 -exec ls -lL {} \; # find / -perm -2000 -exec aclget {} \; Ensure sgid files are part of the operating system software, documented application software, documented utility software, or documented locally developed software. Ensure none are text files or shell programs.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002820: The audit system must be configured to audit all discretionary access control permission modifications.
Check the system's audit configuration. # more /etc/security/audit/events Confirm the following events are configured: FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner. If any of these events are not configured, this is a finding. Check the FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner audit events are defined in the audit classes' stanza classes: of the /etc/security/audit/config file. #more /etc/security/audit/config Make note of the audit class(es) the FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner events are associated with. If the FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner events are not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. If the class(es) the FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner events are not associated with the default user and all the system users in the users: stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Edit /etc/security/audit/events and add the FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner events to the list of audited events. Edit /etc/security/audit/config and add the FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner audit events to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes with the FILE_Acl, FILE_Fchmod, FILE_Fchown, FILE_Mode, and FILE_Owner events to the all users listed in the users: stanza.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003240: The cron.allow file must be owned by root, bin, or sys.
# ls -lL /var/adm/cron/cron.allow If the cron.allow file is not owned by root, sys, or bin, this is a finding.
Discussion
If the owner of the cron.allow file is not set to root, bin, or sys, the possibility exists for an unauthorized user to view or to edit sensitive information.
Fix
# chown root /var/adm/cron/cron.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001280: Manual page files must have mode 0644 or less permissive.
Check the mode of the manual page files. Procedure: # ls -lLR /usr/share/man /usr/share/info /usr/share/infopage If any of the manual page files have a mode more permissive than 0644, this is a finding.
Discussion
If manual pages are compromised, misleading information could be inserted, causing actions that may compromise the system.
Fix
Change the mode of manual page files to 0644 or less permissive. Procedure (example): # chmod 0644 <path>/<manpage>
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN009140: The system must not have the chargen service active.
Check the /etc/inetd.conf file for active TCP and UDP chargen service entries. # grep chargen /etc/inetd.conf |grep -v \# If the chargen service is enabled, this is a finding.
Discussion
When contacted, chargen responds with some random characters. When contacted via UDP, it will respond with a single UDP packet. When contacted via TCP, it will continue spewing characters until the client closes the connection. An easy attack is 'ping-pong' in which an attacker spoofs a packet between two machines running chargen. This will cause them to spew characters at each other, slowing the machines down and saturating the network. The chargen service is unnecessary and provides an opportunity for Denial of Service attack.
Fix
Edit /etc/inetd.conf and comment out the chargen service line for both udp and tcp protocols. Restart the inetd service. #refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003640: The root file system must employ journaling or another mechanism ensuring file system consistency.
Logging should be enabled for those types of files systems that do not turn on logging by default. Procedure: # mount #lsfs JFS, JFS2, VXFS, HFS, XFS, reiserfs, EXT3, and EXT4 all turn logging on by default and will not be a finding. The ZFS file system uses other mechanisms to provide for file system consistency, and will not be a finding. For other file system types, if the root file system does not have the logging option, this is a finding. If the nolog option or the log=NULL option is set on the root file system, this is a finding.
Discussion
File system journaling, or logging, can allow reconstruction of file system data after a system crash, thus, preserving the integrity of data that may have otherwise been lost. Journaling file systems typically do not require consistency checks upon booting after a crash, which can improve system availability. Some file systems employ other mechanisms to ensure consistency which also satisfy this requirement.
Fix
Implement file system journaling for the root file system, or use a file system using other mechanisms to ensure consistency. If the root file system supports journaling, enable it. If the file system does not support journaling or another mechanism to ensure consistency, a migration to a different file system will be necessary.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005510: The SSH client must be configured to only use FIPS 140-2 approved ciphers.
Check the SSH client configuration for allowed ciphers. # grep -i ciphers /etc/ssh/ssh_config | grep -v '^#' If no lines are returned, the returned ciphers list contains any cipher not starting with 3des or aes, this is a finding.
Discussion
DoD information systems are required to use FIPS 140-2 approved ciphers. SSHv2 ciphers meeting this requirement are 3DES and AES.
Fix
Edit /etc/ssh/ssh_config and add or edit the "Ciphers" line. Only include ciphers that start with "3des" or "aes" and do not contain "cbc". For the list of available ciphers for the particular version of your software, consult the ssh_config manpage.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000290: The system must not have unnecessary accounts.
Check the system for unnecessary user accounts. Procedure: # more /etc/passwd Some examples of unnecessary accounts includes guest, uucp, games, news, gopher, ftp, and lp. If any unnecessary accounts are found, this is a finding.
Discussion
Accounts providing no operational purpose provide additional opportunities for system compromise. Unnecessary accounts include user accounts for individuals not requiring access to the system and application accounts for applications not installed on the system.
Fix
Remove all unnecessary accounts, such as games, from the /etc/passwd file before connecting a system to the network. Other accounts, such as news and gopher, that are associated with a service not in use should also be removed. # rmuser -p <username>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008200: If the system is using LDAP for authentication or account information, the LDAP TLS certificate authority file and/or directory (as appropriate) must not have an extended ACL.
Determine the SSL certificate key database file and/or directory. # grep -i '^ldapsslkeyf' /etc/security/ldap/ldap.cfg For each file or directory returned, check the permissions. # aclget < certpath > # aclget < certpath >/< certfile > If extended file permissions are enabled, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Remove the extended ACL from the SSL certificate key database file. # acledit < certpath > # acledit < certpath >/<certfile > Disable the extended file permissions.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003380: The "at" daemon must not execute programs in, or subordinate to, world-writable directories.
List any "at" jobs on the system. Procedure: # ls /var/spool/cron/atjobs /var/spool/atjobs For each "at" job, determine which programs are executed. Procedure: # more <at job file> Check the directory containing each program executed by "at" for world-writable permissions. Procedure: # ls -la <at program file directory> If "at" executes programs in world-writable directories, this is a finding.
Discussion
If "at" programs are located in, or subordinate, to world-writable directories, they become vulnerable to removal and replacement by malicious users or system intruders.
Fix
Remove the world-writable permission from directories containing programs executed by "at". Procedure: # chmod o-w <at program directory>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001740: All global initialization files must be owned by root.
Check the ownership of global initialization files. Procedure: # ls -lL /etc/.login /etc/profile /etc/bashrc /etc/environment /etc/security/environ /etc/security/.profile /etc/csh.login /etc/csh.cshrc If any global initialization file is not owned by root, this is a finding.
Discussion
Global initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the ownership of global initialization files with incorrect ownership. Procedure: # chown bin <global initialization files>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003255: The at.deny file must not have an extended ACL.
Determine if the at.deny file has an extended ACL. #aclget /var/adm/cron/at.deny Verify if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
The at daemon control files restrict access to scheduled job manipulation and must be protected. Unauthorized modification of the at.deny file could result in Denial of Service to authorized at users or provide unauthorized users with the ability to run at jobs.
Fix
Remove the extended ACL from the at.deny file and disable extended permissions. #acledit /var/adm/cron/at.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001901: Local initialization files' library search paths must contain only absolute paths.
Verify local initialization files have library search path containing only absolute paths. # cat /etc/passwd | cut -f 1,1 -d ":" | xargs -n1 -IUSER sh -c 'grep -l LIB ~USER/.*' The LIBPATH and LD_LIBRARY_PATH variables are formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a relative path, and this is a finding.
Discussion
The library search path environment variable(s) contain a list of directories for the dynamic linker to search to find libraries. If this path includes the current working directory or other relative paths, libraries in these directories may be loaded instead of system libraries. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.
Fix
Edit the local initialization file(s) and remove the relative path entry from the library search path.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001373: The /etc/nsswitch.conf file must have mode 0644 or less permissive.
Check the mode of the /etc/nsswitch.conf file. AIX does not use the /etc/nsswitch.conf file. This check is not applicable. Procedure: # ls -l /etc/nsswitch.conf If the file mode is more permissive than 0644, this is a finding.
Discussion
The nsswitch.conf file (or equivalent) configures the source of a variety of system security information including account, group, and host lookups. Malicious changes could prevent the system from functioning or compromise system security.
Fix
Change the mode of the /etc/nsswitch.conf file to 0644 or less permissive. # chmod 0644 /etc/nsswitch.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005550: The SSH daemon must be configured with the Department of Defense (DoD) logon banner.
Verify the SSH daemon is configured for logon warning banners. # grep -i banner /etc/ssh/sshd_config | grep -v '^#' # cat [banner file] Verify the banner configuration line is present and the file it references contains a logon warning banner. Check for either of the following login banners based on the character limitations imposed by the system. An exact match is required. If one of these banners is not displayed, this is a finding. "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details." OR "I've read & consent to terms in IS user agreem't." If the SSH daemon is not configured to display the logon warning banner, this is a finding.
Discussion
Failure to display the DoD logon banner prior to a log in attempt will negate legal proceedings resulting from unauthorized access to system resources. The SSH service must be configured to display the DoD logon warning banner either through the SSH configuration or a wrapper program, such as TCP_WRAPPERS. The SSH daemon may also be used to provide SFTP service. The warning banner configuration for SSH will apply to SFTP.
Fix
Edit the SSH daemon configuration and add (or edit) a banner setting referencing a file containing a logon warning banner. DoD Login Banners: "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details." OR "I've read & consent to terms in IS user agreem't."
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002060: All .rhosts, .shosts, .netrc, or hosts.equiv files must be accessible by only root or the owner.
# find / -type f -name .rhosts # ls -alL /<directorylocation>/.rhosts # find / -type f -name .shosts # ls -alL /<directorylocation>/.shosts # find / -type f -name hosts.equiv # ls -lL /<directorylocation>/hosts.equiv # find / -type f -name shosts.equiv # ls -lL /<directorylocation>/shosts.equiv If the .rhosts, .shosts, hosts.equiv, or shosts.equiv files have permissions greater than 700, this is a finding.
Discussion
If these files are accessible by users other than root or the owner, they could be used by a malicious user to set up a system compromise.
Fix
Ensure the permission for these files is set at 700 or less and the owner is the owner of the home directory that it is in. These files, outside of home directories (other than hosts.equiv which is in /etc and owned by root), have no meaning.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001520: All interactive users' home directories must be group-owned by the home directory owner's primary group.
Check the group ownership for each user in the /etc/passwd file. Procedure: # ls -lLd <user home directory> If any user's home directory is not group-owned by the assigned user's primary group, this is a finding. Home directories for application accounts requiring different group ownership must be documented using site-defined procedures.
Discussion
If the GID of the home directory is not the same as the GID of the user, this would allow unauthorized access to files.
Fix
Change the group owner for user's home directories to the primary group of the assigned user. Procedure: # chgrp groupname directoryname (Replace examples with appropriate group and home directory.) Document all changes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001550: All files and directories contained in user's home directories must be group-owned by a group the home directory's owner is a member.
Check the contents of user home directories for files group-owned by a group of which the home directory's owner is not a member. 1. List the user accounts. # cut -d : -f 1/etc/passwd 2. For each user account, get a list of GIDs for files in the user's home directory. # find < users home directory > -exec ls -lLd 3. Obtain the list of GIDs associated with the user's account. # id < user name > 4. Check the GID lists. If there are GIDs in the file list not present in the user list, this is a finding.
Discussion
If a user's files are group-owned by a group where the user is not a member, unintended users may be able to access them.
Fix
Change the group of a file not group-owned by a group where the home directory's owner is a member. # chgrp [user's primary group] [file with bad group ownership]
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005511: The SSH client must be configured to not use CBC-based ciphers.
Check the SSH client configuration for allowed ciphers. # grep -i ciphers /etc/ssh/ssh_config | grep -v '^#' If no lines are returned, or the returned ciphers list contains any cipher ending with cbc, this is a finding.
Discussion
The Cipher-Block Chaining (CBC) mode of encryption as implemented in the SSHv2 protocol is vulnerable to chosen plain text attacks and must not be used.
Fix
Edit /etc/ssh/ssh_config and add or edit the "Ciphers" line. Only include ciphers that start with "3des" or "aes" and do not contain "cbc". For the list of available ciphers for the particular version of your software, consult the ssh_config manpage.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009320: The system must not have the sprayd service active.
Check the /etc/inetd.conf file for active sprayd service. # grep sprayd /etc/inetd.conf | grep -v \# If the sprayd service is enabled, this is a finding.
Discussion
The sprayd service is sometimes used for network and nfs troubleshooting. The spray service can be used for both buffer overflow and Denial of Service attacks by saturating the network. The sprayd daemon is an unnecessary service.
Fix
Edit the /etc/inetd.conf file and comment out the sprayd service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003470: The at.allow file must be group-owned by system, bin, sys, or cron.
Determine the group owner of the at.allow file. Procedure: # ls -lL /var/adm/cron/at.allow If the group-owner is not bin, sys, system, or cron, this is a finding.
Discussion
If the group-owner of the at.allow file is not set to system, bin, sys, or cron, unauthorized users could be allowed to view or edit the list of users permitted to run at jobs. Unauthorized modification could result in Denial of Service to authorized at users or provide unauthorized users with the ability to run at jobs.
Fix
Change the group owner of the at.allow file to sys, system, bin, or cron. Procedure: # chgrp cron /var/adm/cron/at.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008520: The system must employ a local firewall.
Determine if the system is using a local firewall. # lsfilt # smitty ipsec4 If local firewall is not configured and running, this is a finding.
Discussion
A local firewall protects the system from exposing unnecessary or undocumented network services to the local enclave. If a system within the enclave is compromised, firewall protection on an individual system continues to protect it from attack.
Fix
Configure the system to use a local firewall. Use SMIT to load the IPSEC filesets. #smit install Use SMIT to configure filters. #smit ipsec4
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005460: The system must only use remote syslog servers (log hosts) justified and documented using site-defined procedures.
Examine the syslog.conf file for any references to remote log hosts. # grep -v "^#" /etc/syslog.conf | grep '@' Destination locations beginning with an @ represent log hosts. If the log host name is a local alias, such as log host, consult the /etc/hosts or other name databases as necessary to obtain the canonical name or address for the log host. Determine if the host referenced is a log host documented using site-defined procedures. If an undocumented log host is referenced, this is a finding.
Discussion
If a remote log host is in use and it has not been justified and documented with the IAO, sensitive information could be obtained by unauthorized users without the SA's knowledge. A remote log host is any host to which the system is sending syslog messages over a network.
Fix
Remove, replace, or document the referenced undocumented log host.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003860: The system must not have the finger service active.
# grep -v "^#" /etc/inetd.conf |grep finger If the finger service is not disabled, this is a finding.
Discussion
The finger service provides information about the system's users to network clients. This information could expose information that could be used in subsequent attacks.
Fix
Edit /etc/inetd.conf and comment out the finger service line. Restart the inetd service.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001600: Run control scripts' executable search paths must contain only absolute paths.
Verify run control scripts' library search paths. Procedure: # grep -r PATH /etc/rc* This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is a finding. If an entry begins with a character other than a slash (/), this is a relative path, and this is a finding.
Discussion
The executable search path (typically the PATH environment variable) contains a list of directories for the shell to search to find executables. If this path includes the current working directory or other relative paths, executables in these directories may be executed instead of system commands. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, or two consecutive colons, this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.
Fix
Edit the run control script and remove the relative path entry from the executable search path variable.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001780: Global initialization files must contain the mesg -n or mesg n commands.
Check global initialization files for the presence of mesg -n or mesg n. Procedure: # grep "mesg" /etc/.login /etc/profile /etc/bashrc /etc/environment /etc/security/environ /etc/security/.profile /etc/csh.login /etc/csh.cshrc If no global initialization files contain mesg -n or mesg n, this is a finding.
Discussion
If the mesg -n or mesg n command is not placed into the system profile, messaging can be used to cause a Denial of Service attack.
Fix
Edit /etc/profile or another global initialization script and add the mesg -n command.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN005504: The SSH daemon must only listen on management network addresses unless authorized for uses other than management.
Check the SSH daemon configuration for listening network addresses. # grep -i Listen /etc/ssh/sshd_config | grep -v '^#' If no configuration is returned, or if a returned Listen configuration contains addresses not designated for management traffic, this is a finding.
Discussion
The SSH daemon should only listen on network addresses designated for management traffic. If the system has multiple network interfaces and SSH listens on addresses not designated for management traffic, the SSH service could be subject to unauthorized access. If SSH is used for purposes other than management, such as providing an SFTP service, the list of approved listening addresses may be documented.
Fix
Edit the SSH daemon configuration to specify listening network addresses designated for management traffic.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002000: There must be no .netrc files on the system.
Check the system for the existence of any .netrc files. Procedure: # find / -name .netrc If any .netrc file exists, this is a finding.
Discussion
Unencrypted passwords for remote FTP servers may be stored in .netrc files. Policy requires passwords be encrypted in storage and not used in access scripts.
Fix
Remove the .netrc file(s). Procedure: # rm .netrc
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003650: All local file systems must employ journaling or another mechanism ensuring file system consistency.
Determine if the local file systems employ journaling or another mechanism ensuring file system consistency. Procedure: List all local file system mount points. #df -l #lsfs < each file system returned> If any file systems are not jfs or jfs2, this is a finding.
Discussion
File system journaling, or logging, can allow reconstruction of file system data after a system crash, thus preserving the integrity of data that may have otherwise been lost. Journaling file systems typically do not require consistency checks upon booting after a crash, which can improve system availability. Some file systems employ other mechanisms to ensure consistency which also satisfy this requirement.
Fix
Convert local file systems to use journaling or another mechanism ensuring file system consistency.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN006240: The system must not run an Internet Network News (INN) server.
# ps -ef | egrep "innd|nntpd" If an INN server is running, this is a finding.
Discussion
Internet Network News (INN) servers access Usenet newsfeeds and store newsgroup articles. INN servers use the Network News Transfer Protocol (NNTP) to transfer information from the Usenet to the server and from the server to authorized remote hosts. If this function is necessary to support a valid mission requirement, its use must be authorized and approved in the system accreditation package.
Fix
Disable the INN server.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009180: The system must not have the tool-talk database server (ttdbserver) service active.
Check the /etc/inetd.conf file for active ttdbserver service. # grep 'rpc\.ttdbserver' /etc/inetd.conf |grep -v \# If the ttdbserver service is enabled, this is a finding.
Discussion
The ttdbserver service for CDE is an unnecessary service that runs as root and might be compromised.
Fix
Edit /etc/inetd.conf and comment out ttdbserver service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003609: The system must ignore IPv4 ICMP redirect messages.
# /usr/sbin/no -o ipignoreredirects If the value returned is not 1, this is a finding.
Discussion
ICMP redirect messages are used by routers to inform hosts a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
Fix
Configure the system to ignore IPv4 ICMP redirect messages. #/usr/sbin/no -p -o ipignoreredirects=1
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002400: The system must be checked weekly for unauthorized setuid files, as well as, unauthorized modification to authorized setuid files.
Determine if a weekly automated or manual process is used to generate a list of setuid files on the system and compare it with the prior list. If no such process is in place, this is a finding.
Discussion
Files with the setuid bit set will allow anyone running these files to be temporarily assigned the UID of the file. While many system files depend on these attributes for proper operation, security problems can result if setuid is assigned to programs that allow reading and writing of files, or shell escapes.
Fix
Establish a weekly automated or manual process to generate a list of setuid files on the system and compare it with the prior list. To create a list of setuid files use the following command. # find / -perm -4000 > setuid-file-list
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003608: Proxy ARP must not be enabled on the system.
Determine if the system has proxy ARP enabled. Check Content: Check the system for non-local published ARP entries. # arp -a If any entries are listed as published, this is a finding.
Discussion
Proxy ARP allows a system to respond to ARP requests on one interface on behalf of hosts connected to another interface. If this function is enabled when not required, addressing information may be leaked between the attached network segments.
Fix
Remove any non-local published ARP entries. # arp -d < host > Check system initialization scripts for any commands configuring published ARP entries (such as "arp -s <host> <addr> pub") and remove them.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0210: The system must provide protection from Internet Control Message Protocol (ICMP) attacks on TCP connections.
Check the value of the tcp_icmpsecure parameter. # /usr/sbin/no -o tcp_icmpsecure If the value returned is not 1, this is a finding.
Discussion
The ICMP attacks may be of the form of ICMP source quench attacks and Path MTU Discovery (PMTUD) attacks. If this network option tcp_icmpsecure is turned on, the system does not react to ICMP source quench messages. This will protect against ICMP source quench attacks. The payload of the ICMP message is tested to determine if the sequence number of the TCP header portion of the payload is within the range of acceptable sequence numbers. This will mitigate PMTUD attacks to a large extent.
Fix
Set the tcp_icmpsecure parameter to 1. # /usr/sbin/no -p -o tcp_icmpsecure=1
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009200: The system must not have the daytime service active.
Check the /etc/inetd.conf file for TCP and UDP daytime service. #grep daytime /etc/inetd.conf | grep -v \# If the daytime service is enabled, this is a finding.
Discussion
The daytime service runs as root from the inetd daemon and can provide an opportunity for Denial of Service PING or PING-PONG attacks. The daytime service is unnecessary and it increases the attack vector of the system.
Fix
Edit /etc/inetd.conf and comment out daytime service lines for both TCP and UDP protocols. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004580: The system must not use .forward files.
Search for any .forward files on the system. # find / -name .forward -print This is considered a finding if any .forward files are found on the system.
Discussion
The .forward file allows users to automatically forward mail to another system. Use of .forward files could allow the unauthorized forwarding of mail and could potentially create mail loops which could degrade system performance.
Fix
Remove .forward files from the system.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006570: The file integrity tool must be configured to verify ACLs.
If using AIDE, verify the configuration contains the acl option for all monitored files and directories. Here is an example AIDE configuration fragment. SampleRule = p+i+l+n+u+g+s+m+c+acl+xattrs+sha256 /bin SampleRule If the acl option is not present, this is a finding. If using a different file integrity tool, check the configuration per tool documentation.
Discussion
ACLs can provide permissions beyond those permitted through the file mode and must be verified by file integrity tools.
Fix
If using AIDE, edit the configuration and add the acl option for all monitored files and directories. If using a different file integrity tool, configure ACL checking per the tool's documentation.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN002870: The system must be configured to send audit records to a remote audit server.
Ask the SA to provide information on the remote logging of audit records. Verify the configuration described is functioning. If no method of remote logging of audit records is in place or functioning, this is a finding. Methods of remote audit record logging will be site-specific and may depend on the use of third-party tools. One possible method with AIX is the use of the audit streams facility such as: Verify "streammode = on" in /etc/security/audit/config. Check that /etc/security/audit/streamcmds sends stream logs to the syslog facility with an entry such as: /usr/sbin/auditstream | auditpr -v | /usr/bin/logger -p local7.info & Check that the /etc/syslog.conf file is configured to send local7.info to a remote server with an entry such as: local7.info @logserver
Discussion
Audit records contain evidence that can be used in the investigation of compromised systems. To prevent this evidence from compromise, it must be sent to a separate system continuously. Methods for sending audit records include, but are not limited to, system audit tools used to send logs directly to another host or through the system's syslog service to another host.
Fix
Configure the system to send audit records to a remote system. The actual method is left to site discretion and may involve the use of third-party products. One method for performing remote audit logging involves streaming audit records to syslog and using syslog to send the records to another system. Enable stream mode by editing the /etc/security/audit/config and set streammode = on. Edit /etc/security/audit/streamcmds to send stream logs to the syslog facility with an entry such as: /usr/sbin/auditstream | auditpr -v | /usr/bin/logger -p local7.info & Edit the /etc/syslog.conf file to configure syslog to send local7.info to a remote server with an entry such as: Local7.info @logserver
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003730: The inetd.conf file, xinetd.conf file, and the xinetd.d directory must be group-owned by bin, sys, or system.
Check the group ownership of the inetd and xinetd configuration files, and xinetd directory. Procedure: # ls -alL /etc/inetd.conf /etc/xinetd.conf /etc/xinetd.d If a file or directory is not group-owned by bin, sys, or system, this is a finding.
Discussion
Failure to give ownership of sensitive files or utilities to system groups may provide unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the group ownership of the inetd configuration file. Procedure: # chgrp system /etc/inetd.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005560: The system must be configured with a default gateway for IPv4 if the system uses IPv4, unless the system is a router.
Check the system for an IPv4 default route. Procedure: # netstat -r |grep default If a default route is not defined, this is a finding.
Discussion
If a system has no default gateway defined, the system is at increased risk of man-in-the-middle, monitoring, and Denial of Service attacks.
Fix
Set a default gateway for IPv4. # smitty route OR # route add 0 < ip address of gateway >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006230: Samba must be configured to use encrypted passwords.
Check the encryption setting the Samba configuration. # grep -i 'encrypt passwords' /usr/lib/smb.conf If the setting is not present, or not set to yes, this is a finding.
Discussion
Samba must be configured to protect authenticators. If Samba passwords are not encrypted for storage, plain-text user passwords may be read by those with access to the Samba password file.
Fix
Edit the smb.conf file and change the encrypt passwords setting to yes. # vi /usr/lib/smb.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003500: Process core dumps must be disabled unless needed.
# lsuser -a core ALL If any user does not have a value of core = 0, this is a finding.
Discussion
Process core dumps contain the memory in use by the process when it crashed. Process core dump files can be of significant size and their use can result in file systems filling to capacity, which may result in Denial of Service. Process core dumps can be useful for software debugging.
Fix
# chsec -f /etc/security/limits -s default -a core=0
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000800: The system must prohibit the reuse of passwords within five iterations.
Procedure: #lsuser -a histsize ALL If the returned histsize for any user is less than 5, this is a finding.
Discussion
If a user, or root, used the same password continuously or was allowed to change it back shortly after being forced to change it to something else, it would provide a potential intruder with the opportunity to keep guessing at one user's password until it was guessed correctly.
Fix
Use the chsec command to configure the system to prohibit the reuse of passwords within five iterations. # chsec -f /etc/security/user -s default -a histsize=5 # chuser histsize=5 < user id >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002715: System audit tool executables must be owned by root.
Determine if the system audit tool executables are owned by root. Audit tools include, but are not limited to, audit, auditcat, auditconv, auditpr, auditselect, auditstream, auditbin, and auditmerge. Procedure: ls -lL `which <audit tool executable>` If any system audit tool executable is not owned by root, this is a finding.
Discussion
To prevent unauthorized access or manipulation of system audit logs, the tools for manipulating those logs must be protected.
Fix
Change the owner of the system audit tool executables to root. #chown root <system audit tool executable>
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN002740: The audit system must be configured to audit file deletions.
Check the system audit configuration to determine if failed attempts to access files and programs are audited. # more /etc/security/audit/events If auditing of the FILE_Unlink or FS_Rmdir events is not configured, this is a finding. If no results are returned, this is a finding. Check the FILE_Unlink and FS_Rmdir audit event(s) are defined in the audit classes' stanza classes: of the /etc/security/audit/config file. #more /etc/security/audit/config Make note of the audit class(es) that the File_Unlink and FS_Rmdir events are associated with. If the FILE_Unlink and FS_Rmdir events are not associated with any audit classes in the classes: stanza this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. #more /etc/security/audit/config If the class(es) that the FILE_Unlink and FS_Rmdir events are not associated with the default user and all the system users in the users: stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Edit /etc/security/audit/events and add the FILE_Unlink or FS_Rmdir events to the list of audited events. Edit /etc/security/audit/config and add the FILE_Unlink and FS_Rmdir audit events to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes containing the FILE_Unlink and FS_Rmdir events to the all users listed in the users: stanza.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005524: The SSH daemon must not permit GSSAPI authentication unless needed.
Ask the SA if GSSAPI authentication is used for SSH authentication to the system. If so, this is not applicable. Check the SSH daemon configuration for the GSSAPI authentication setting. # grep -i GSSAPIAuthentication /etc/ssh/sshd_config | grep -v '^#' If the setting is present and set to "yes", this is a finding. If the setting is absent or set to "no", this is not a finding.
Discussion
GSSAPI authentication is used to provide additional authentication mechanisms to applications. Allowing GSSAPI authentication through SSH exposes the system’s GSSAPI to remote hosts, increasing the attack surface of the system. GSSAPI authentication must be disabled unless needed.
Fix
Edit /etc/ssh/sshd_config and remove the GSSAPIAuthentication setting or change the value to "no".
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003050: Crontab files must be group-owned by system, cron, or the crontab creator's primary group.
Check the group ownership of the crontab files. # ls -lL /var/spool/cron/crontabs/ If the group owner is not system, cron, or the crontab owner's primary group, this is a finding.
Discussion
To protect the integrity of scheduled system jobs and prevent malicious modification to these jobs, crontab files must be secured.
Fix
Change the group owner of the crontab file to system, cron, or the crontab's primary group. Procedure: # chgrp cron [crontab file]
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002230: All shell files must not have extended ACLs.
Check the permissions of each shell referenced in /etc/shells. Procedure: # cat /etc/shells For each shell listed, run aclget <shell path> #aclget <shell> Check the permissions of each shell referenced in /etc/security/login.cfg. Procedure: #grep shells /etc/security/login.cfg For each shell listed, run aclget <shell path> # aclget <shell> Otherwise, check any shells found on the system. # find / -name "*sh #aclget <directory>/<file> If extended permissions are enabled on any shell, this is a finding.
Discussion
Shells with world/group write permissions give the ability to maliciously modify the shell to obtain unauthorized access.
Fix
Remove the extended ACL from the shell file(s) and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003601: TCP backlog queue sizes must be set appropriately.
# /usr/sbin/no -o clean_partial_conns If the value returned is 0, this is a finding.
Discussion
To provide some mitigation to TCP DoS attacks, the clear_partial_conns parameter must be enabled.
Fix
# /usr/sbin/no -po clean_partial_conns=1
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003850: The telnet daemon must not be running.
Consult vendor documentation to determine the method for determining if the telnet daemon is running. If the system uses inetd, use the following procedure. # grep -v '^#' /etc/inetd.conf | grep telnet If an entry is returned, the telnet daemon is running. If the telnet daemon is running, this is a finding.
Discussion
The telnet daemon provides a typically unencrypted remote access service which does not provide for the confidentiality and integrity of user passwords or the remote session. If a privileged user were to log on using this service, the privileged user password could be compromised.
Fix
Edit the /etc/inetd.conf file and comment out the telnet line. Reload the inetd process. # refresh -s inetd
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN004660: The SMTP service must not have the EXPN feature active.
Perform the following to determine if EXPN is disabled: # telnet localhost 25 expn root If the command does not return a 500 error code of command unrecognized, this is a finding. OR Locate the sendmail.cf configuration file by: # find / -name sendmail.cf -print # grep -v "^#" <sendmail.cf location> |grep -i privacyoptions The O PrivacyOptions should have the noexpn or the goaway option (covering both noexpn and novrfy). If the EXPN command is not disabled, this is a finding.
Discussion
The SMTP EXPN function allows an attacker to determine if an account exists on a system, providing significant assistance to a brute force attack on user accounts. EXPN may also provide additional information concerning users on the system, such as the full names of account owners.
Fix
Edit the sendmail.cf file and add or edit the following line: O PrivacyOptions=goaway Restart the Sendmail service.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN008140: If the system is using LDAP for authentication or account information, the TLS certificate authority file and/or directory (as appropriate) must be owned by root.
Determine the SSL Certificate database file and/or directory. # grep -i '^ldapsslkeyf' /etc/security/ldap/ldap.cfg For each file or directory returned, check the ownership. # ls -lLd <certpath> If the owner of any file or directory is not root, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Change the ownership of the SSL key database file or directory. # chown root <certpath>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000250: The time synchronization configuration file (such as /etc/ntp.conf) must be owned by root.
Determine the owner of the ntp.conf file. # ls -l /etc/ntp.conf If the owner is not root, this is a finding.
Discussion
A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. If an illicit time source is used for synchronization, the integrity of system logs and the security of the system could be compromised. If the configuration files controlling time synchronization are not owned by a system account, unauthorized modifications could result in the failure of time synchronization.
Fix
Change the owner of the ntp.conf file. # chown root ntp.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006150: The /usr/lib/smb.conf file must not have an extended ACL.
Check the group ownership of the Samba configuration file. # aclget /usr/lib/smb.conf If the extended attributes are not disabled, this is a finding.
Discussion
Excessive permissions could endanger the security of the Samba configuration file and, ultimately, the system and network.
Fix
Remove the extended ACL from the /usr/lib/smb.conf file and change extended attributes to disabled. #acledit /usr/lib/smb.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006640: The system must use and update a DoD-approved virus scan program.
Check for the existence of the McAfee command line scan tool to be executed daily in the cron file. Additional tools specific for each operating system are also available and will have to be manually reviewed if installed. In addition, the definitions file should not be older than 14 days. Check if uvscan is scheduled to run: # grep uvscan /var/spool/cron/crontabs/* Perform the following command to ensure the virus definition signature files are not older than 14 days. # ls -la clean.dat names.dat scan.dat If a virus scanner is not being run daily or the virus definitions are older than 14 days, this is a finding.
Discussion
Virus scanning software can be used to protect a system from penetration by computer viruses and to limit their spread through intermediate systems. Virus scanning software is available to DoD on the JTF-GNO web site. The virus scanning software should be configured to perform scans dynamically on accessed files. If this capability is not available, the system must be configured to scan, at a minimum, all altered files on the system on a daily basis. If the system processes inbound SMTP mail, the virus scanner must be configured to scan all received mail.
Fix
Install McAfee command line virus scan tool, or an appropriate alternative from https://www.jtfgno.mil. Ensure the virus signature definition files are no older than 14 days. Updates are also available from https://www.jtfgno.mil. Ensure the command line virus scan tool is run on a regular basis using a utility, such as cron.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003490: The at.deny file must be group-owned by system, bin, sys, or cron.
Determine the group owner of the at.deny file. Procedure: # ls -lL /var/adm/cron/at.deny If the group owner is not bin, sys, system, or cron, this is a finding.
Discussion
If the group owner of the at.deny file is not set to system, bin, sys, or cron, unauthorized users could be allowed to view or edit sensitive information contained within the file. Unauthorized modification could result in Denial of Service to authorized at users or provide unauthorized users with the ability to run at jobs.
Fix
Change the group owner of the at.deny file to bin, sys, system, or cron. Procedure: # chgrp cron /var/adm/cron/at.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000452: The system must display the date and time of the last successful account login upon login.
Determine if the system displays the date and time of the last successful login upon logging in. This can be accomplished by logging into the system and verifying whether or not the necessary information is displayed. If the system does not provide this information upon login, this is a finding. Verify the SSH daemon is configured to display last login information. # cat /etc/ssh/sshd_config | grep -i PrintLastLog If PrintLastLog is disabled, this is a finding.
Discussion
Providing users with feedback on when account accesses last occurred facilitates user recognition and reporting of unauthorized account use.
Fix
Configure the system to display the date and time of the last successful login upon logging in. Consult OS documentation for the configuration procedure. Enable PrintLastLog in the SSH daemon. To enable PrintLastLog in the SSH daemon, remove any comment disabling this option from /etc/ssh/sshd_config. The line should look like: "PrintLastLog yes". Restart sshd. # kill -1 <PID of sshd>
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001369: The /etc/hosts file must not have an extended ACL.
Verify /etc/hosts has no extended ACL. Check to see if extended permissions are disabled. Procedure: #aclget /etc/hosts If extended permissions are not disabled, this is a finding.
Discussion
The /etc/hosts file (or equivalent) configures local host name to IP address mappings that typically take precedence over DNS resolution. If this file is maliciously modified, it could cause the failure or compromise of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.
Fix
Remove the extended ACL from the /etc/hosts file and disable extended permissions. #acledit /etc/hosts
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001890: Local initialization files must not have extended ACLs.
Check user home directories for local initialization files with extended ACLs. Procedure: # cat /etc/passwd | cut -f 6,6 -d ":" | xargs -n1 -IDIR ls -le DIR/.login DIR/.cshrc DIR/.logout DIR/.profile DIR/.bash_profile DIR/.bashrc DIR/.bash_logout DIR/.env DIR/.dtprofile DIR/.dispatch DIR/.emacs DIR/.exrc Procedure: #aclget <directory>/<file> and check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Local initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.
Fix
Remove the extended ACL from the local initialization file(s) and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0220: The system must provide protection for the TCP stack against connection resets, SYN, and data injection attacks.
Check the value of the tcp_tcpsecure parameter. # /usr/sbin/no -o tcp_tcpsecure If the value returned is not 7, this is a finding.
Discussion
The tcp_tcpsecure parameter provides protection for TCP connections from fake SYN's, fake RST, and data injections on established connections. The first vulnerability involves sending a fake SYN to an established connection to abort the connection. The second vulnerability involves sending a fake RST to an established connection to abort the connection. The third vulnerability involves injecting fake data in an established TCP connection.
Fix
Set the tcp_tcpsecure parameter to 7. # /usr/sbin/no -p -o tcp_tcpsecure=7
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001680: All system start-up files must be group-owned by sys, bin, other, or system.
Check run control scripts' group ownership. Procedure: # ls -lL /etc/rc* If any run control script is not group-owned by sys, bin, other, or system, this is a finding.
Discussion
If system start-up files do not have a group owner of a system group, the files may be modified by malicious users or intruders.
Fix
Change the group ownership of the run control script(s) with incorrect group ownership. Procedure: # chgrp sys <run control script>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007860: The system must ignore IPv6 ICMP redirect messages.
Determine if the system is configured to ignore IPv6 ICMP redirect messages. If it is not, this is a finding. # /usr/sbin/no -o ipignoreredirects If the value returned is not 1, this is a finding.
Discussion
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
Fix
Configure the system to ignore IPv6 ICMP redirect messages. # /usr/sbin/no -p -o ipignoreredirects=1
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002752: The audit system must be configured to audit account disabling.
Determine if the system is configured to audit account disabling. Procedure: # more /etc/security/audit/events If auditing of the USER_Change and USER_Locked events are not configured, this is a finding. Check the USER_Change and USER_Locked audit event(s) are defined in the audit classes' stanza classes: of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config Make note of the audit class(es) the USER_Change and USER_Locked events are associated with. If the USER_Change and USER_Locked events are not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config If the class(es) the USER_Change and USER_Locked events are not associated with the default user and all the system users in the users: stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Configure the system to audit account disabling. Edit /etc/security/audit/events and add the USER_Change and USER_Locked events to the list of audited events. Edit /etc/security/audit/config and add the USER_Change and USER_Locked audits event to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes with the USER_Change and USER_Locked events to the all users listed in the users: stanza.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN002540: All public directories must be group-owned by system or an application group.
Check the group ownership of public directories. Procedure: # find / -type d -perm -1002 -exec ls -ld {} \; If any public directory is not group-owned by system, sys, bin, or an application group, this is a finding.
Discussion
If a public directory has the sticky bit set and is not group-owned by a system GID, unauthorized users may be able to modify files created by others. The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage (e.g., /tmp) and for directories requiring global read/write access.
Fix
Change the group ownership of the public directory. Procedure: # chgrp system /tmp (Replace system with a different system group and/or /tmp with a different public directory as necessary.)
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001490: User home directories must not have extended ACLs.
Verify user home directories have no extended ACLs. Procedure: # cat /etc/passwd | cut -f 6,6 -d ":" | xargs -n1 aclget Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Excessive permissions on home directories allow unauthorized access to user files.
Fix
Remove the extended ACL from the user home directory and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN006140: The /usr/lib/smb.conf file must have mode 0644 or less permissive.
Check the mode of the smb.conf file. Procedure: # ls -lL /usr/lib/smb.conf If the smb.conf has a mode more permissive than 0644, this is a finding.
Discussion
If the smb.conf file has excessive permissions, the file may be maliciously modified and the Samba configuration could be compromised.
Fix
Change the mode of the smb.conf file to 0644 or less permissive. Procedure: # chmod 0644 /usr/lib/smb.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002980: The cron.allow file must have mode 0640 or less permissive.
Check mode of the cron.allow file. Procedure: # ls -lL /var/adm/cron/cron.allow If the file has a mode more permissive than 0640, this is a finding.
Discussion
A cron.allow file that is readable and/or writable by other than root could allow potential intruders and malicious users to use the file contents to help discern information, such as who is allowed to execute cron programs, which could be harmful to overall system and network security.
Fix
Change the mode of the cron.allow file to 0640. Procedure: # chmod 0640 /var/adm/cron/cron.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005305: The SNMP service must use only SNMPv3 or its successors.
Determine if the system's SNMP service only uses SNMPv3 or its successors. Consult vendor documentation to determine if earlier versions of SNMP are supported and what configuration is necessary to enable or disable the protocols. Snmpd version 1 was the only version available in AIX versions prior to AIX 5.2. #which snmpd #ls -l <path to snmpd> If the results are not /usr/sbin/snmpdv3e or /usr/sbin/snpdv3ne this is an earlier version of the protocol used by the service, this is a finding.
Discussion
SNMP Versions 1 and 2 are not considered secure. Without the strong authentication and privacy provided by the SNMP Version 3 User-based Security Model (USM), an attacker or other unauthorized users may gain access to detailed system management information and use the information to launch attacks against the system.
Fix
Configure the system's SNMP service to only use SNMPv3 with encryption or its successors. The SNMP version supporting encryption is an installable fileset on the expansion cd as fileset 'snmp.crypto'. Enable snmpv3 with encryption. # snmpv3_ssw -e
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003520: The kernel core dump data directory must be owned by root.
Determine the core file copy location. #sysdumpdev -l | grep -i "core dir" Check the ownership of the kernel core dump data directory. # ls -ld < dump file location > If the kernel core dump data directory is not owned by root, this is a finding.
Discussion
Kernel core dumps may contain the full contents of system memory at the time of the crash. As the system memory may contain sensitive information, it must be protected accordingly. If the kernel core dump data directory is not owned by root, the core dumps contained in the directory may be subject to unauthorized access.
Fix
Change the owner of the kernel core dump data directory to root. # chown root /var/adm/ras Supplementary Information: The location of the kernel dump area should be moved out of /var/adm/ras. This directory may be world read/writeable. A suggestion would be to create /var/adm/kcore; chown root:sys /var/adm/kcore; chmod 700 /var/adm/kcore. Change where the system copies its kernel core files to. sysdumpdev -d /var/adm/kcore
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003000: Cron must not execute group-writable or world-writable programs.
List all cronjobs on the system. Procedure: # ls /var/spool/cron/crontabs/ If cron jobs exist under any of the above directories search for programs executed by cron. Procedure: # more <cron job file> Determine if the file is group-writable or world-writable. Procedure: # ls -la <cron program file> If cron executes group-writable or world-writable files, this is a finding.
Discussion
If cron executes group-writable or world-writable programs, there is a possibility that unauthorized users could manipulate the programs with malicious intent. This could compromise system and network security.
Fix
Remove the world-writable and group-writable permissions from the cron program file(s) identified. # chmod go-w <cron program file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005365: The snmpd.conf file must be group-owned by bin, sys, or system.
Determine the group owner of the SNMP configuration files. Procedure: # ls -lL /etc/snmpd.conf /etc/snmpdv3.conf If the file is not group owned by bin, sys, or system, this is a finding.
Discussion
The snmpd.conf file contains authenticators and must be protected from unauthorized access and modification. If the file is not group-owned by a system group, it may be subject to access and modification from unauthorized users.
Fix
Change the group owner of the SNMP configuration files. Procedure: # chgrp system /etc/snmpd.conf # chgrp system /etc/snmpdv3.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005840: The NFS server must be configured to restrict file system access to local hosts.
Check the permissions on exported NFS file systems. Procedure: # exportfs -v If the exported file systems do not contain the rw or ro options specifying a list of hosts or networks, this is a finding.
Discussion
The NFS access option limits user access to the specified level. This assists in protecting exported file systems. If access is not restricted, unauthorized hosts may be able to access the system's NFS exports.
Fix
Edit /etc/exports and add ro and/or rw options (as appropriate) specifying a list of hosts or networks which are permitted access. Re-export the file systems.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001475: The /etc/group file must not contain any group password hashes.
Check the /etc/group file for password hashes. Procedure: # cut -d : -f 2 /etc/group | egrep -v '^(x|!)$' If any password hashes are returned, this is a finding. If no password hashes are returned, there is no finding.
Discussion
Group passwords are typically shared and should not be used. Additionally, if password hashes are readable by non-administrators, the passwords are subject to attack through lookup tables or cryptographic weaknesses in the hashes.
Fix
Edit /etc/group and change the password field to an exclamation point (!) to lock the group password.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005480: The syslog daemon must not accept remote messages unless it is a syslog server documented using site-defined procedures.
Verify syslogd is running with the -R option. #ps -ef | grep syslogd | grep -v grep If the -R option is not present, this is a finding.
Discussion
Unintentionally running a syslog server that accepts remote messages puts the system at increased risk. Malicious syslog messages sent to the server could exploit vulnerabilities in the server software itself, could introduce misleading information in to the system's logs, or could fill the system's storage leading to a Denial of Service.
Fix
Change the syslogd arguments in the src subsystem control and restart the syslogd daemon. # chssys -s syslogd -a '-R' # stopsrc -s syslogd # startsrc -s syslogd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001340: NIS/NIS+/yp files must be group-owned by sys, bin, other, or system.
Check the group ownership of the NIS files. Procedure: # ls -lRa /var/nis /var/yp /usr/lib/nis /usr/lib/netsvc/yp If the file group owner is not sys, bin, or system, this is a finding.
Discussion
NIS/NIS+/yp files are part of the system's identification and authentication processes and are, therefore, critical to system security. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the group owner of the NIS files to sys, bin, system, or other. Procedure: # chgrp system < directory>/< file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003410: The at directory must not have an extended ACL.
Check the permissions of the file. #aclget /var/spool/cron/atjobs Verify if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
If the at directory has an extended ACL, unauthorized users could be allowed to view or to edit files containing sensitive information within the at directory. Unauthorized modifications could result in Denial of Service to authorized at jobs.
Fix
Remove the extended ACL from the at directory and disable extended permissions. #acledit /var/spool/cron/atjobs
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002720: The audit system must be configured to audit failed attempts to access files and programs.
Check the system audit configuration to determine if failed attempts to access files and programs are audited. Check system activities (events) to audit are listed in the /etc/security/audit/events file. Procedure: # more /etc/security/audit/events If the FILE_Open event is not configured, this is a finding. Check the FILE_Open audit event is defined in the audit classes' stanza classes: of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config Make note of the audit class(es) that the FILE_Open event is associated with. If the FILE_Open event is not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config If the class(es) the FILE_Open event is(/are) not associated with the default user and all the system users in the users: stanza, this is a finding. Supplementary Information: Successful setup of AIX auditing requires several files and stanza's to be correctly configured. 1. The /etc/security/audit/events must have the system call defined. 2. The /etc/security/audit/config has 2 stanzas that need to be configured a. "classes:" stanza. Each entry in this stanza defines two things. The first is the name of a class to group the events to be audited on. The class is linked to users of the system for auditing. The second is the event(s) to be audited in this class: stanza. Example: classes: DISA_CLASS = FILE_Open, File_Unlink, FS_Rmdir b. "users:" stanza. There are two options of specifying what users audit on. The first is to explicitly spell out user names. EXAMPLE: users: root = DISA_CLASS The second is to specify a default catching all users not listed elsewhere in the users: stanza EXAMPLE users: root = DISA_CLASS default = DISA_CLASS 3. An approach to setup auditing to meet STIG requirements would be to create class stanza with all audit events that are required. The users: stanza would then be populated with the root user, any other user ids with special requirements and finally a default user. 4. The /usr/lib/security/mkuser.default file can have under the users: stanza an entry auditclasses = class(es) of events to be audited for each new user added to the system.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Edit /etc/security/audit/events and add the FILE_Open event to the list of audited events. Edit /etc/security/audit/config and add the FILE_Open audit event to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes that have the FILE_Open event to the users listed in the users: stanza.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003180: The cronlog file must have mode 0600 or less permissive.
Check the mode of the cron log file. # ls -lL /var/adm/cron/log If the mode is more permissive than 0600, this is a finding.
Discussion
Cron logs contain reports of scheduled system activities and must be protected from unauthorized access or manipulation.
Fix
Change the mode of the cron log file. # chmod 0600 /var/adm/cron/log
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001300: Library files must have mode 0755 or less permissive.
Check the mode of library files. Procedure: # ls -lLR /usr/lib /lib If any of the library files have a mode more permissive than 0755, this is a finding.
Discussion
Unauthorized access could destroy the integrity of the library files.
Fix
Change the mode of library files to 0755 or less permissive. Procedure (example): # chmod 0755 <path>/<library-file> NOTE: Library files should have an extension of .a or .so (a=archive, so=shared object) extension, possibly followed by a version.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001290: All manual page files must not have extended ACLs.
Determine if any manual page files on the system have extended ACLs. Check to see if extended permissions are disabled. #aclget < directory >/< file > If extended permissions are not disabled, this is a finding.
Discussion
If manual pages are compromised, misleading information could be inserted, causing actions that may compromise the system.
Fix
Remove the extended ACLs from system manual page file(s) and disable extended permissions. #acledit < directory >/< file >
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000560: The system must not have accounts configured with blank or null passwords.
Verify no accounts have blank passwords. # pwdck -n ALL If any account with a blank password is found, this is a finding.
Discussion
If an account is configured for password authentication but does not have an assigned password, it may be possible to log into the account without authentication. If the root user is configured without a password, the entire system may be compromised. For user accounts not using password authentication, the account must be configured with a password lock value instead of a blank or null value.
Fix
Remove or configure a password for any account with a blank password. # passwd <user id> # smitty passwd To remove an account with a blank password. # smitty rmuser
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN002200: All shell files must be owned by root or bin.
Obtain a list of system shells from /etc/security/login.cfg and check the ownership of these shells. Procedure: #grep shells /etc/security/login.cfg | grep -v \* | cut -f 2 -d = | sed s/,/\ /g | xargs -n1 ls -l If any shell is not owned by root or bin, this is a finding. Obtain a list of system shells from /etc/shells and check the ownership of these shells. Procedure: #cat /etc/shells | xargs -n1 ls -l If any shell is not owned by root or bin, this is a finding.
Discussion
If shell files are owned by users other than root or bin, they could be modified by intruders or malicious users to perform unauthorized actions.
Fix
Change the ownership of the shell with incorrect ownership. # chown root < shell >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005160: Any X Windows host must write .Xauthority files.
Check for .Xauthority files being utilized by looking for such files in the home directory of a user that uses X. Procedure: # cd ~someuser # ls -la .Xauthority If the .Xauthority file does not exist, ask the SA if the user is using X Windows. If the user is utilizing X Windows and the .Xauthority file does not exist, this is a finding.
Discussion
.Xauthority files ensure the user is authorized to access the specific X Windows host. If .Xauthority files are not used, it may be possible to obtain unauthorized access to the X Windows host.
Fix
Ensure the X Windows host is configured to write .Xauthority files into user home directories. Edit the Xaccess file. Ensure the line that writes the .Xauthority file is uncommented.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000790: The system must prevent the use of dictionary words for passwords.
Procedure: #lsuser -a dictionlist ALL If the dictionlist is blank or not listed, the system is not checking against a dictionary of words that are not to be used for passwords. This is a finding.
Discussion
An easily guessable password provides an open door to any external or internal malicious intruder. Many computer compromises occur as the result of account name and password guessing. This is generally done by someone with an automated script using repeated logon attempts until the correct account and password pair is guessed. Utilities, such as cracklib, can be used to validate that passwords are not dictionary words and meet other criteria during password changes.
Fix
Install the default dictionary of words from the 'bos.data' fileset with smitty or installp. # smitty installp #installp bos.data Customize or modify the dictionary in /usr/share/dict/words as necessary. #vi /usr/share/dict/words Add a dictionary list to /etc/security/user file with the chsec command. #chsec -f /etc/security/user -s default -a dictionlist=/usr/share/dict/words
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001140: System files and directories must not have uneven access permissions.
Check system directories for uneven file permissions. Procedure: # ls -lL /etc /bin /usr/bin /usr/lbin /usr/ucb /sbin /usr/sbin Uneven file permissions exist if the file owner has less permissions than the group or other user classes. If any of the files in the above listed directories contain uneven file permissions, this is a finding.
Discussion
Discretionary access control is undermined if users, other than a file owner, have greater access permissions to system files and directories than the owner.
Fix
Change the mode of files with uneven permissions so owners do not have less permission than group or world users.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000280: Direct logins must not be permitted to shared, default, application, or utility accounts.
Use the last command to check for multiple accesses to an account from different workstations/IP addresses. If users log directly onto accounts, rather than using the su command from their own named account to access them, this is a finding (such as logging directly on to Oracle). Also, ask the SA or the IAO if shared accounts are logged into directly or if users log on to an individual account and switch user to the shared account. # last <unix account> Shared or Application accounts can have direct login disabled by setting the rlogin parameter to false in the users stanza of the /etc/security/user file. #lsuser -a rlogin < user_id > If users log directly on to shared accounts, this is a finding.
Discussion
Shared accounts (accounts where two or more people log in with the same user identification) do not provide identification and authentication. There is no way to provide for non-repudiation or individual accountability.
Fix
Use the switch user (su) command from a named account login to access shared accounts. Maintain audit trails to identify the actual user of that account name. Document requirements and procedures for users/administrators to log into their own accounts first and then switch user (su) to the account that must be shared. Direct login to shared or application accounts can be prevented by setting the rlogin = false in the accounts stanza of the /etc/security/user file. Additional hardening of the shared/application accounts can be done with the sugroups = in the accounts stanza of the /etc/security/user file. #chuser rlogin=false < user id >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004510: The SMTP service log file must not have an extended ACL.
Examine /etc/syslog.conf and determine the log file(s) receiving logs for mail.crit, mail.debug, mail.*, or *.crit. Check the permissions on these log files. #aclget [log file] Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
If the SMTP service log file has an extended ACL, unauthorized users may be allowed to access or to modify the log file.
Fix
Remove the extended ACL from the SMTP service log file and disable extended permissions. #acledit [ log file ]
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004640: The SMTP service must not have a uudecode alias active.
Check the SMTP service for an active decode command. Procedure: # telnet localhost 25 decode If the command does not return a 500 error code of command unrecognized, this is a finding.
Discussion
A common configuration for older Mail Transfer Agents (MTAs) includes an alias for the decode user. All mail sent to this user is sent to the uudecode program, which automatically converts and stores files. By sending mail to decode or uudecode aliases present on some systems, a remote attacker may be able to create or overwrite files on the remote host. This could possibly be used to gain remote access.
Fix
Disable mail aliases for decode and uudecode. If the /etc/aliases or /usr/lib/aliases (mail alias) file contains entries for these programs, remove them or disable them by placing # at the beginning of the line, and then executing the "newaliases" command. For more information on mail aliases, refer to the man page for aliases. Disabled aliases would be similar to the examples below: # decode: |/usr/bin/uudecode # uudecode: |/usr/bin/uuencode -d
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN004980: The FTP daemon must be configured for logging or verbose mode.
Perform: # grep ftpd /etc/inetd.conf, Check the line for ftpd to check if the -l argument. If the ftpd is invoked without the -l argument, this is a finding. Check the /etc/syslog.conf file for daemon.info or *.info. # more /etc/syslog.conf If daemon.info or *.info is not being logged, this is a finding.
Discussion
The -l option allows logging of connections. This extra logging makes it possible to easily track which files are being transferred onto or from a system. If they are not configured, the only option for tracking is the audit files. The audit files are much harder to read. If auditing is not properly configured, then there would be no record at all of the file transfer transactions.
Fix
Edit the /etc/inetd.conf file and add the -l argument to the ftpd service line. # vi /etc/inetd.conf Restart inetd.conf # refresh -s inetd Add daemon.info or *.info to the /etc/syslog.conf file. #vi /etc/syslog.conf *.info /var/log/syslog Restart the syslog daemon. # refresh -s syslogd
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003280: Access to the at utility must be controlled via the at.allow and/or at.deny file(s).
Check for the existence of at.allow and at.deny files. # ls -lL /var/adm/cron/at.allow # ls -lL /var/adm/cron/at.deny If neither file exists, this is a finding.
Discussion
The at facility selectively allows users to execute jobs at deferred times. It is usually used for one-time jobs. The at.allow file selectively allows access to the at facility. If there is no at.allow file, there is no ready documentation of who is allowed to submit at jobs.
Fix
Create at.allow and/or at.deny files containing appropriate lists of users to be allowed or denied access to the "at" daemon.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006340: Files in /etc/news must be owned by root or news.
Check the ownership of the files in /etc/news. Procedure: # ls -al /etc/news If any files are not owned by root or news, this is a finding.
Discussion
If critical system files are not owned by a privileged user, system integrity could be compromised.
Fix
Change the ownership of the files in /etc/news to root or news. Procedure: # chown root /etc/news/*
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004930: The ftpusers file must be group-owned by bin, sys, or system.
Check the group ownership of the ftpusers file. Procedure: # ls -lL /etc/ftpusers If the file is not group-owned by bin, sys, or system, this is a finding.
Discussion
If the ftpusers file is not group-owned by a system group, an unauthorized user may modify the file to allow unauthorized accounts to use FTP.
Fix
Change the group owner of the ftpusers file. Procedure: # chgrp system /etc/ftpusers
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007920: The system must not forward IPv6 source-routed packets.
# /usr/sbin/no -o ip6srcrouteforward If the value returned is not 0, this is a finding.
Discussion
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router.
Fix
Configure the system so it does not forward IPv6 source-routed packets. # /usr/sbin/no -p -o ip6srcrouteforward=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000700: User passwords must be changed at least every 60 days.
Check the maxage field for each user. The field represents the number of weeks a password is valid. Procedure: # /usr/sbin/lsuser -a maxage ALL If the maxage field is 0 or greater than 8 for any user, this is a finding.
Discussion
Limiting the lifespan of authenticators limits the period of time an unauthorized user has access to the system while using compromised credentials and reduces the period of time available for password-guessing attacks to run against a single password.
Fix
Use the chsec command to set the maxage field to 8 for each user. # chsec -f /etc/security/user -s default -a maxage=8 # chuser maxage=8 < user id >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004880: The ftpusers file must exist.
Check for the existence of the ftpusers file. # ls -l /etc/ftpusers If the ftpusers file does not exist, this is a finding.
Discussion
The ftpusers file contains a list of accounts not allowed to use FTP to transfer files. If this file does not exist, then unauthorized accounts can utilize FTP.
Fix
Create a /etc/ftpusers file containing a list of accounts not authorized for FTP.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002420: Removable media, remote file systems, and any file system not containing approved setuid files must be mounted with the nosuid option.
Check /etc/filesystems and verify the nosuid mount option is used on file systems mounted from removable media, network shares, or any other file system not containing approved setuid or setgid files. Each file system stanza must contain a device special file and may additionally contain all of the following fields type = , options = , and check = . # more /etc/filesystems # lsfs If any of these files systems do not mount with the nosuid option, it is a finding.
Discussion
The nosuid mount option causes the system to not execute setuid files with owner privileges. This option must be used for mounting any file system not containing approved setuid files. Executing setuid files from untrusted file systems, or file systems not containing approved setuid files, increases the opportunity for unprivileged users to attain unauthorized administrative access.
Fix
Edit /etc/filesystems and add the options = nosuid to the stanza of file system mounted from removable media or network shares, and any file system not containing approved setuid or setgid files. OR Add the nosuid option with the chfs command. # chfs -a options=nosuid <filesystem>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003430: The "at" directory must be group-owned by system, bin, sys, or cron.
Check the group ownership of the file. Procedure: # ls -ld /var/spool/cron/atjobs If the file is not group-owned by bin, sys, system, or cron, this is a finding.
Discussion
If the group of the "at" directory is not system, bin, sys, or cron, unauthorized users could be allowed to view or edit files containing sensitive information within the directory.
Fix
Change the group ownership of the file to bin, sys, system, or cron. Procedure: # chgrp cron /var/spool/cron/atjobs
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0200: The system must not allow directed broadcasts to gateway.
Check the directed_broadcast option. # /usr/sbin/no -o directed_broadcast If the value returned is not 0, this is a finding.
Discussion
Disabling directed broadcast prevents packets directed to a gateway to be broadcasted on a remote network.
Fix
Configure directed_broadcast to 0. # /usr/sbin/no -p -o directed_broadcast=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006235: Samba must be configured to not allow guest access to shares.
Check the encryption setting the Samba configuration. # grep -i 'guest ok' /usr/lib/smb.conf If the setting exists and is set to yes, this is a finding.
Discussion
Guest access to shares permits anonymous access and is not permitted.
Fix
Edit the smb.conf file and change the guest ok setting to no. # vi /usr/lib/smb.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002860: Audit logs must be rotated daily.
Check for any crontab entries that rotate audit logs. Procedure: # crontab -l If such a cron job is found, this is not a finding. Otherwise, query the SA. If there is a process automatically rotating audit logs, this is not a finding. If the SA manually rotates audit logs, this is still a finding, because if the SA is not there, it will not be accomplished. If the audit output is not archived daily, to tape or disk, this is a finding. This can be ascertained by looking at the audit log directory and, if more than one file is there, or if the file does not have today's date, this is a finding.
Discussion
Rotate audit logs daily to preserve audit file system space and to conform to the DoD/DISA requirement. If it is not rotated daily and moved to another location, then there is more of a chance for the compromise of audit data by malicious users.
Fix
Configure a cron job or other automated process to rotate the audit logs on a daily basis.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000750: The system must require at least four characters be changed between the old and new passwords during a password change.
Check the value of the mindiff parameter. Procedure: #lsuser -a mindiff ALL If any users mindiff is less than 4, this is a finding.
Discussion
To ensure password changes are effective in their goals, the system must ensure old and new passwords have significant differences. Without significant changes, new passwords may be easily guessed based on the value of a previously compromised password.
Fix
Use the chsec command to change mindiff to 4. # chsec -f /etc/security/user -s default -a mindiff=4 # chuser mindiff=4 < user id >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005526: The SSH daemon must not permit Kerberos authentication unless needed.
Ask the SA if Kerberos authentication is used by the system. If it is, this is not applicable. Check the SSH daemon configuration for the Kerberos authentication setting. # grep -i KerberosAuthentication /etc/ssh/sshd_config | grep -v '^#' If the setting is present and set to "yes", this is a finding. If the setting is missing or set to "no", this is not a finding.
Discussion
Kerberos authentication for SSH is often implemented using GSSAPI. If Kerberos is enabled through SSH, the SSH daemon provides a means of access to the system's Kerberos implementation. Vulnerabilities in the system's Kerberos implementation may then be subject to exploitation. To reduce the attack surface of the system, the Kerberos authentication mechanism within SSH must be disabled for systems not using this capability.
Fix
Edit the /etc/ssh/sshd_config file and remove the KerberosAuthentication setting or change the value of the setting to "no".
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001430: The /etc/security/passwd file must not have an extended ACL.
Verify the /etc/security/passwd file has no extended ACL and check if extended permissions are disabled. Procedure: #aclget /etc/security/passwd If extended permissions are not disabled, this is a finding.
Discussion
The /etc/security/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification. The file also contains password hashes which must not be accessible to users other than root.
Fix
Remove the extended ACL from the /etc/security/passwd file and disable extended permissions. #acledit /etc/security/passwd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003440: "At" jobs must not set the umask to a value less restrictive than 077.
Determine what "at" jobs exist on the system. Procedure: # ls /var/spool/cron/atjobs /var/spool/atjobs If there are no "at" jobs present, this is not applicable. Determine if any of the "at" jobs or any scripts referenced execute the umask command. Check for any umask setting more permissive than 077. # grep umask <at job or referenced script> If any "at" job or referenced script sets umask to a value more permissive than 077, this is a finding.
Discussion
The umask controls the default access mode assigned to newly created files. An umask of 077 limits new files to mode 700 or less permissive. Although umask is often represented as a 4-digit number, the first digit representing special access modes is typically ignored or required to be 0.
Fix
Edit "at" jobs or referenced scripts to remove umask commands setting umask to a value less restrictive than 077.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000540: Users must not be able to change passwords more than once every 24 hours.
Check the minage field for each user. # /usr/sbin/lsuser -a minage ALL If the minage field is less than 1 for any user, this is a finding.
Discussion
The ability to change passwords frequently facilitates users reusing the same password. This can result in users effectively never changing their passwords. This would be accomplished by users changing their passwords when required and then immediately changing it to the original value.
Fix
Use SMIT or the chsec command to set the minimum password age to 1 week. # chsec -f /etc/security/user -s default -a minage=1 # chsec -f /etc/security/user -s <user id> -a minage=1 OR # smitty chuser
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003270: The cron.deny file must be group-owned by system, bin, sys, or cron.
Determine the cron.deny file's group owner. Procedure: # ls -lL /var/adm/cron/cron.deny If the file is not group-owned by system, bin, sys, or cron, this is a finding.
Discussion
Cron daemon control files restrict the scheduling of automated tasks and must be protected. Unauthorized modification of the cron.deny file could result in Denial of Service to authorized cron users or could provide unauthorized users with the ability to run cron jobs.
Fix
Change the group owner of the cron.deny file to sys, system, bin, or cron. Procedure: # chgrp cron /var/adm/cron/cron.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008540: The system's local firewall must implement a deny-all, allow-by-exception policy.
Determine if the system's local firewall implements a deny-all, allow-by-exception policy. View the firewall (filter rules) with smit or lsfilt commands. # smitty ipsec4 # lsfilt If there is not a deny-all, allow-by-exception policy, this is a finding.
Discussion
A local firewall protects the system from exposing unnecessary or undocumented network services to the local enclave. If a system within the enclave is compromised, firewall protection on an individual system continues to protect it from attack.
Fix
Configure the system's local firewall to implement a deny-all, allow-by-exception policy. Firewall rules can be added and activated with SMIT ipsec4 or genfilt command. #smitty ipsec4
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001200: All system command files must have mode 0755 or less permissive.
Check the permissions for files in /etc, /bin, /usr/bin, /usr/lbin, /usr/ucb, /sbin, and /usr/sbin. Procedure: # ls -lL /etc /bin /usr/bin /usr/lbin /usr/ucb /sbin /usr/sbin If any command file is listed and has a mode more permissive than 0755, this is a finding. NOTE: Elevate to Severity Code I if any command file listed is world-writable.
Discussion
Restricting permissions will protect system command files from unauthorized modification. System command files include files present in directories used by the operating system for storing default system executables and files present in directories included in the system's default executable search paths.
Fix
Change the mode for system command files to 0755 or less permissive. Procedure: # chmod 0755 <filename>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008620: System BIOS or system controllers supporting password protection must have administrator accounts/passwords configured, and no others.
Ask the SA if a password has been given to the Service processors ADMIN account. If a password has not been assigned to the service processor, this is a finding.
Discussion
A system's BIOS or system controller handles the initial startup of a system and its configuration must be protected from unauthorized modification. When the BIOS or system controller supports the creation of user accounts or passwords, such protections must be used and accounts/passwords only assigned to system administrators. Failure to protect BIOS or system controller settings could result in Denial of Service or compromise of the system resulting from unauthorized configuration changes.
Fix
Access the system's service processor. Set a supervisor/administrator password if one has not been set. Disable a user-level password if one has been set.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003480: The at.deny file must be owned by root, bin, or sys.
# ls -lL /var/adm/cron/at.deny If the at.deny file is not owned by root, sys, or bin, this is a finding.
Discussion
If the owner of the at.deny file is not set to root, bin, or sys, unauthorized users could be allowed to view or edit sensitive information contained within the file.
Fix
Change the owner of the at.deny file. # chown root /var/adm/cron/at.deny
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001870: Local initialization files must be group-owned by the user's primary group or root.
Check user home directories for local initialization files group-owned by a group other than the user's primary group or root. 1. List user accounts and their primary GID. # cut -d : -f 1,4 /etc/passwd 2. Check local initialization files for each user. # ls -alL ~USER/.login ~USER/.cshrc ~USER/.logout ~USER/.profile ~USER/.bash_profile ~USER/.bashrc ~USER/.bash_logout ~USER/.env ~USER/.dtprofile ~USER/.dispatch ~USER/.emacs ~USER/.exrc 3. If any file is not group-owned by root or the user's primary GID, this is a finding.
Discussion
Local initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.
Fix
Change the group owner of the local initialization file to the user's primary group, or root. # chgrp [USER's primary GID] ~USER/[local initialization file]
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003250: The cron.allow file must be group-owned by system, bin, sys, or cron.
Determine the group owner of the cron.allow file. Procedure: # ls -lL /var/adm/cron/cron.allow If the group owner is not bin, sys, system, or cron, this is a finding.
Discussion
If the group of the cron.allow is not set to system, bin, sys, or cron, the possibility exists for an unauthorized user to view or edit the list of users permitted to use cron. Unauthorized modification of this file could cause Denial of Service to authorized cron users or provide unauthorized users with the ability to run cron jobs.
Fix
Change the group owner of the cron.allow file to bin, sys, system, or cron. Procedure: # chgrp cron /var/adm/cron/cron.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001320: NIS/NIS+/yp files must be owned by root, sys, or bin.
Perform the following to check NIS file ownership. # ls -lRa /var/nis /var/yp /usr/lib/nis /usr/lib/netsvc/yp If the file ownership is not root, sys, or bin, this is a finding.
Discussion
NIS/NIS+/yp files are part of the system's identification and authentication processes and are, therefore, critical to system security. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the owner of the NIS files to root, sys, or bin. Procedure (example): # chown root < directory>/< file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004700: The Sendmail service must not have the wizard backdoor active.
Locate the sendmail.cf configuration file and check for wiz configuration. Procedure: # find / -name sendmail.cf -print # grep -v "^#" <sendmail.cf location> |grep -i wiz If an entry is found for wiz, this is a finding.
Discussion
Very old installations of the Sendmail mailing system contained a feature whereby a remote user connecting to the SMTP port can enter the WIZ command and be given an interactive shell with root privileges.
Fix
If the WIZ command is enabled on Sendmail, it should be disabled by adding this line to the sendmail.cf configuration file (it must be typed in uppercase). OW* For the change to take effect, kill the Sendmail process, refreeze the sendmail.cf file, and restart the Sendmail process.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN008480: The system must have USB Mass Storage disabled unless needed.
If the system uses USB mass storage, this is not applicable. # lslpp -l | grep -e devices.usbif.010100 -e devices.usbif.08025 -e devices.usbif.080400 If these filesets are installed on the system, USB mass storage is enabled and this is a finding.
Discussion
USB is a common computer peripheral interface. USB devices may include storage devices that could be used to install malicious software on a system or exfiltrate data.
Fix
Disable USB mass storage on the system by using SMIT to remove the following filesets. devices.usbif.010100 devices.usbif.08025002 devices.usbif.080400 # smitty remove
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN006060: The system must not run Samba unless needed.
Check the system for a running Samba server. Procedure: # ps -ef |grep smbd If the Samba server is running, ask the SA if the Samba server is operationally required. If it is not, this is a finding.
Discussion
Samba is a tool used for the sharing of files and printers between Windows and UNIX operating systems. It provides access to sensitive files and, therefore, poses a security risk if compromised.
Fix
If there is no functional need for Samba and the daemon is running, disable the daemon by killing the process ID as noted from the output of ps -ef |grep smbd. The utility should also be removed or not installed if there is no functional requirement.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002990: The cron.allow file must not have an extended ACL.
Check the permissions of the cron.allow file. #aclget /var/adm/cron/cron.allow Verify if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
A cron.allow file that is readable and/or writable by other than root could allow potential intruders and malicious users to use the file contents to help discern information, such as who is allowed to execute cron programs, which could be harmful to overall system and network security.
Fix
Remove the extended ACL from the cron.allow file and disable extended permissions. #acledit /var/adm/cron/cron.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003510: Kernel core dumps must be disabled unless needed.
Determine if kernel core dumps are enabled on the system. #sysdumpdev -l Look at both the primary and secondary dump devices. If either the primary or secondary dump device is not /dev/sysdumpnull, this is a finding.
Discussion
Kernel core dumps may contain the full contents of system memory at the time of the crash. Kernel core dumps may consume a considerable amount of disk space and may result in Denial of Service by exhausting the available space on the target file system. The kernel core dump process may increase the amount of time a system is unavailable due to a crash. Kernel core dumps can be useful for kernel debugging.
Fix
Disable kernel core dumps on the system by setting primary and secondary dump devices to sysdumpnull. #sysdumpdev -P -p /dev/sysdumpnull #sysdumpdev -P -s /dev/sysdumpnull
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001363: The /etc/resolv.conf file must be group-owned by bin, sys, or system.
Check the group ownership of the resolv.conf file. Procedure: # ls -lL /etc/resolv.conf If the file is not group-owned by bin, sys, or system, this is a finding.
Discussion
The resolv.conf (or equivalent) file configures the system's DNS resolver. DNS is used to resolve host names to IP addresses. If DNS configuration is modified maliciously, host name resolution may fail or return incorrect information. DNS may be used by a variety of system security functions, such as time synchronization, centralized authentication, and remote system logging.
Fix
Change the group owner of the /etc/resolv.conf file to bin, sys, or system. Procedure: # chgrp system /etc/resolv.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000410: The FTPS/FTP service on the system must be configured with the Department of Defense (DoD) login banner.
FTP to the system. # ftp localhost Check for either of the following login banners based on the character limitations imposed by the system. An exact match is required. If one of these banners is not displayed, this is a finding. If the system does not run the FTP service, this is not applicable. DoD Login Banners: "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details." OR "I've read & consent to terms in IS user agreem't."
Discussion
Failure to display the login banner prior to a logon attempt will negate legal proceedings resulting from unauthorized access to system resources. NOTE: SFTP and FTPS are encrypted alternatives to FTP and should be used in place of FTP. SFTP is implemented by the SSH service and uses its banner configuration.
Fix
Configure the system to display one of the DoD login banners (based on the character limitations imposed by the system) prior to any FTP login attempt. Add a banner file to the system with the DoD login banner. #vi /etc/herald <Add DoD banner to file> #chmod 644 /etc/herald #chown root:system /etc/herald Add a herald line to the /etc/ftpaccess.ctl file. #vi /etc/ftpaccess.ctl <add/update line in /etc/ftpaccess.ctl> herald: /etc/herald #chown root:system /etc/ftpaccess.ctl #chmod 640 /etc/ftpaccess.ctl DoD Login Banners: "You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions: -The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations. -At any time, the USG may inspect and seize data stored on this IS. -Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose. -This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy. -Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details." OR "I've read & consent to terms in IS user agreem't."
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005600: IP forwarding for IPv4 must not be enabled, unless the system is a router.
#no -o ipforwarding If the value returned is not 0, this is a finding.
Discussion
If the system is configured for IP forwarding and is not a designated router, it could be used to bypass network security by providing a path for communication not filtered by network devices.
Fix
Disable IPv4 forwarding on the system. #no -p -o ipforwarding=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003190: The cron log files must not have extended ACLs.
#aclget /var/adm/cron/log Verify if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Cron logs contain reports of scheduled system activities and must be protected from unauthorized access or manipulation.
Fix
Remove the extended ACL from the cronlog file and disable extended permissions. #acledit /var/adm/cron/log
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005880: The NFS server must not allow remote root access.
Determine if the NFS server is exporting with the root access option. Procedure: # exportfs -v | grep "root=" If an export with the root option is found, this is a finding.
Discussion
If the NFS server allows root access to local file systems from remote hosts, this access could be used to compromise the system.
Fix
Edit /etc/exports and remove the root= option for all exports. Re-export the file systems.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003980: The traceroute command must be group-owned by sys, bin, or system.
Check the group ownership of the traceroute file. Procedure: # ls -lL /usr/bin/traceroute If the traceroute command is not group-owned by sys, bin, or system, this is a finding.
Discussion
If the group owner of the traceroute command has not been set to a system group, unauthorized users could have access to the command and use it to gain information regarding a network's topology inside of the firewall. This information may allow an attacker to determine trusted routers and other network information possibly leading to system and network compromise.
Fix
Change the group owner of the traceroute command to sys, bin, or system. Procedure: # chgrp system /usr/bin/traceroute
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003780: The services file must have mode 0444 or less permissive.
Check the mode of the services file. Procedure: # ls -lL /etc/services If the services file has a mode more permissive than 0444, this is a finding.
Discussion
The services file is critical to the proper operation of network services and must be protected from unauthorized modification. Unauthorized modification could result in the failure of network services.
Fix
Change the mode of the services file to 0444 or less permissive. Procedure: # chmod 0444 /etc/services
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003770: The services file must be group-owned by bin, sys, or system.
Check the group ownership of the services file. Procedure: # ls -lL /etc/services If the file is not group-owned by bin, sys, or system, this is a finding.
Discussion
Failure to give ownership of system configuration files to root or a system group provides the designated owner and unauthorized users with the potential to change the system configuration which could weaken the system's security posture.
Fix
Change the group owner of the services file. Procedure: # chgrp system /etc/services
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003040: Crontabs must be owned by root or the crontab creator.
List all crontabs on the system. # ls -lL /var/spool/cron/crontabs/ If any crontab is not owned by root or the creating user, this is a finding.
Discussion
To protect the integrity of scheduled system jobs and prevent malicious modification to these jobs, crontab files must be secured.
Fix
Change the crontab owner to root or the crontab creator. # chown root <crontab file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002960: Access to the cron utility must be controlled using the cron.allow and/or cron.deny file(s).
Check for the existence of the cron.allow and cron.deny files. # ls -lL /var/adm/cron/cron.allow # ls -lL /var/adm/cron/cron.deny If neither file exists, this is a finding.
Discussion
The cron facility allows users to execute recurring jobs on a regular and unattended basis. The cron.allow file designates accounts allowed to enter and execute jobs using the cron facility. If neither cron.allow nor cron.deny exists, then any account may use the cron facility. This may open the facility up for abuse by system intruders and malicious users.
Fix
Create /var/adm/cron/cron.allow and/or /var/adm/cron/cron.deny with appropriate content.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000900: The root user's home directory must not be the root directory (/).
Determine if root is assigned a home directory other than / by listing its home directory. Procedure: # grep "^root" /etc/passwd | awk -F":" '{print $6}' If the root user home directory is /, this is a finding.
Discussion
Changing the root home directory to something other than / and assigning it a 0700 protection makes it more difficult for intruders to manipulate the system by reading the files that root places in its default directory. It also gives root the same discretionary access control for root's home directory as for the other plain user home directories.
Fix
The root home directory should be something other than / (such as /root). Procedure: # mkdir /root # chown root /root # chgrp sys /root # chmod 700 /root # cp -r /.??* /root/. Then, edit the passwd file and change the root home directory to /root. The cp -r /.??* command copies all files and subdirectories of file names that begin with "." into the new root directory, which preserves the previous root environment. Must be in the "/" directory when executing the "cp" command.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001240: System files, programs, and directories must be group-owned by a system group.
Check the group ownership of system files, programs, and directories. Procedure: # ls -lLa /etc /bin /usr/bin /usr/lbin /usr/ucb /sbin /usr/sbin If any system file, program, or directory is not group-owned by a system group, this is a finding. For this check, the system-provided "ipsec" group is also acceptable.
Discussion
Restricting permissions will protect the files from unauthorized modification.
Fix
Change the group owner of system files to a system group. Procedure: # chgrp sys /path/to/system/file (System groups other than sys may be used.)
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003522: The kernel core dump data directory must have mode 0700 or less permissive.
Determine the core file copy location. # sysdumpdev -l | grep "core dir" Determine the mode of the kernel core dump data directory. # ls -lLd < directory > If the mode is more permissive than 0700, this is a finding.
Discussion
Kernel core dumps may contain the full contents of system memory at the time of the crash. As the system memory may contain sensitive information, it must be protected accordingly. If the mode of the kernel core dump data directory is more permissive than 0700, unauthorized users may be able to view or to modify kernel core dump data files.
Fix
Change the mode of the kernel core dump data directory to 0700. # chmod 0700 < directory >
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001170: All files and directories must have a valid group owner.
Determine if any file on the system does not have a valid group owner. # find / -nogroup -print If any such files are found, this is a finding.
Discussion
Files without a valid group owner may be unintentionally inherited if a group is assigned the same GID as the GID of the files without a valid group owner.
Fix
Change the group owner for each file without a valid group owner. # chgrp <a-valid-group> /tmp/a-file-without-a-valid-group-owner
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006600: The system's access control program must log each system access attempt.
Normally, TCPD logs to the mail facility in /etc/syslog.conf. Determine if syslog is configured to log events by TCPD. Procedure: # more /etc/syslog.conf Look for entries similar to the following: mail.debug /var/adm/maillog mail.none /var/adm/maillog mail.* /var/log/mail auth.info /var/log/messages The above entries would indicate mail alerts are being logged. If no entries for mail exist, then TCPD is not logging and this is a finding.
Discussion
If access attempts are not logged, then multiple attempts to log on to the system by an unauthorized user may go undetected.
Fix
Configure the access restriction program to log every access attempt. Ensure the implementation instructions for TCP_WRAPPERS are followed, so system access attempts are logged into the system log files. If an alternate application is used, it must support this function.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009220: The system must not have the dtspc service active.
Check the /etc/inetd.conf for the dtspc service. #grep dtspcd /etc/inetd.conf | grep -v \# If the dtspc service is enabled, this is a finding.
Discussion
This service is started automatically by the inetd daemon with root permission in response to a CDE client requesting a process to be started on the daemon’s host system. Running the dtscp service is unnecessary and it increases the attack vector of the system.
Fix
Edit /etc/inetd.conf and comment out dtspc service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000360: Group Identifiers (GIDs) reserved for system accounts must not be assigned to non-system groups.
# more /etc/passwd Confirm all accounts with a GID of 99 and below (499 and below for Linux) are used by a system account. If a GID reserved for system accounts, 0 - 99 (0 - 499 for Linux), is used by a non-system account, this is a finding.
Discussion
Reserved GIDs are typically used by system software packages. If non-system groups have GIDs in this range, they may conflict with system software, possibly leading to the group having permissions to modify system files.
Fix
Change the primary group GID numbers for non-system accounts with reserved primary group GIDs (those less or equal to 99 in general, or 499 for Linux). # smitty chuser
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005740: The NFS export configuration file must be owned by root.
Check the owner of the exports file. Example: # ls -lL /etc/exports If the export configuration file is not owned by root, this is a finding.
Discussion
Failure to give ownership of the NFS export configuration file to root provides the designated owner and possible unauthorized users with the potential to change system configuration which could weaken the system's security posture.
Fix
Change the owner of the exports file to root. Example: # chown root /etc/exports
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002718: System audit tool executables must not have extended ACLs.
Determine if system audit tool executables have extended ACLs Audit tools include, but are not limited to audit, auditcat, auditconv, auditpr, auditselect, auditstream, auditbin, and auditmerge. Procedure: #aclget <system audit tool executable> Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
To prevent unauthorized access or manipulation of system audit logs, the tools for manipulating those logs must be protected.
Fix
Remove the extended ACL from the system audit tool executable(s) and disable extended permissions. #acledit <system audit tool executable>
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000380: All Group Identifiers (GIDs) referenced in the /etc/passwd file must be defined in the /etc/group file.
Perform the following to ensure there are no GIDs referenced in /etc/passwd not defined in /etc/group: # usrck -n ALL If GIDs referenced in /etc/passwd are not defined in /etc/group are returned, this is a finding.
Discussion
If a user is assigned the GID of a group that does not exist on the system, and a group with that GID is subsequently created, the user may have unintended rights to the group.
Fix
Add a group to the system for each GID referenced without a corresponding group. # smitty mkgroup
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003110: Cron and crontab directories must not have extended ACLs.
Check the permissions of the crontab directories. # ls -lL /var/spool/cron/crontabs # aclget < crontab > # aclget /var/spool/cron Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
To protect the integrity of scheduled system jobs and to prevent malicious modification to these jobs, crontab files must be secured. ACLs on cron and crontab directories may provide unauthorized access to these directories. Unauthorized modifications to these directories or their contents may result in the addition of unauthorized cron jobs or deny service to authorized cron jobs.
Fix
Remove the extended ACL from the crontab file(s) and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008050: If the system is using LDAP for authentication or account information, the /etc/ldap.conf file (or equivalent) must not contain passwords.
Examine the LDAP configuration file(s). #grep bindpwd: /etc/security/ldap/ldap.cfg If the returned entry has an unencrypted password (not like "bindpwd:{DES}"), this is a finding. If the LDAP configuration file contains an encrypted password accessible by regular users on the system, this is a finding. #ls -l /etc/security/ldap/ldap.cfg Check for unencrypted SSL keyfile password. #grep '^ldapsslkeypwd' /etc/security/ldap/ldap.cfg If the returned entry has an unencrypted password (not like "ldapsslkeypwd:{DES}"), this is a finding.
Discussion
The authentication of automated LDAP connections between systems must not use passwords since more secure methods are available, such as PKI and Kerberos. Additionally, the storage of unencrypted passwords on the system is not permitted.
Fix
Remove any passwords from LDAP configuration files. The bindpw (bind password) can be encrypted with the mksecldap command. #mksecldap Stash the SSL key database file with the gsk7cmd or ikeyman commands. #gsk7cmd < or > ikeyman Comment out the ldapsslpwd line to use stashed password. The password stash file must reside in the same directory as the SSL key database, and must have the same name as the key database, but with an extension of .sth instead of .kdb.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002753: The audit system must be configured to audit account termination.
Determine if the system is configured to audit account termination. Procedure: # more /etc/security/audit/events If auditing of the USER_Remove event is not configured, this is a finding. Verify the USER_Remove audit event is defined in the audit classes' stanza classes: of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config Make note of the audit class(es) the USER_Remove event is associated with. If the USER_Remove event is not associated with any audit classes in the classes: stanza, this is a finding. Verify that the audit class is associated with the default user and all other user ids listed in the 'users:' stanza of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config If the class(es) that the USER_Remove event is not associated with the default user and all the system users in the users: stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.
Fix
Configure the system to audit account termination. Edit /etc/security/audit/events and add the USER_Remove event to the list of audited events Edit /etc/security/audit/config and add the USER_Remove audit event to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes with the USER_Remove event to the all users listed in the users: stanza.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001980: The .rhosts, .shosts, hosts.equiv, shosts.equiv, /etc/passwd, /etc/shadow, and/or /etc/group files must not contain a plus (+) without defining entries for NIS+ netgroups.
Check system configuration files for plus (+) entries. Procedure: # find / -name .rhosts # cat /<directorylocation>/.rhosts | grep -v "^#" | grep "\+" # find / -name .shosts # cat /<directorylocation>/.shosts | grep -v "^#" | grep "\+" # find / -name hosts.equiv # cat /<directorylocation>/hosts.equiv | grep -v "^#" | grep "\+" # find / -name shosts.equiv # cat /<directorylocation>/shosts.equiv | grep -v "^#" | grep "\+" # cat /etc/passwd | grep -v "^#" | grep "\+" # cat /etc/security/passwd | grep -v "^#" | grep "\+" # cat /etc/group | grep -v "^#" | grep "\+" If the .rhosts, .shosts, hosts.equiv, shosts.equiv, /etc/passwd, /etc/shadow, and/or /etc/group files contain a plus (+) and do not define entries for NIS+ netgroups, this is a finding.
Discussion
A plus (+) in system accounts files causes the system to lookup the specified entry using NIS. If the system is not using NIS, no such entries should exist.
Fix
Edit the .rhosts, .shosts, hosts.equiv, shosts.equiv, /etc/passwd, /etc/security/passwd, and/or /etc/group files and remove entries containing a plus (+).
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001800: All skeleton files (typically those in /etc/skel) must have mode 0644 or less permissive.
Check skeleton files permissions. Procedure: # ls -l /etc/security/.profile If a skeleton file has a mode more permissive than 0644, this is a finding. Check the mkuser.sys file. The /etc/security/mkuser.sys is a script containing items used in creation of users' ~/.profile files. This script needs to be both protected from unauthorized modification, but also needs to be executable, therefore the permissions need to be at the mode of 755. #ls -l /etc/security/mkuser.sys If the mkuser.sys file has a mode more permissive than 0755, this is a finding.
Discussion
If the skeleton files are not protected, unauthorized personnel could change user startup parameters and possibly jeopardize user files.
Fix
Change the mode of skeleton files with incorrect mode. # chmod 0644 /etc/security/.profile #chmod 0755 /etc/security/mkuser.sys
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009210: The system must not have the discard service active.
Check the /etc/inetd.conf file for TCP and UDP discard service entries. #grep discard /etc/inetd.conf | grep -v \# If the discard service is active, this is a finding.
Discussion
The discard service runs as root from the inetd server and can be used in Denial of Service attacks. The discard service is unnecessary and it increases the attack vector of the system.
Fix
Edit /etc/inetd.conf and comment out the discard service line for both TCP and UDP protocols. Restart the inetd service. #refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003300: The at.deny file must not be empty if it exists.
# more /var/adm/cron/at.deny If the at.deny file exists and is empty, this is a finding.
Discussion
On some systems, if there is no at.allow file and there is an empty at.deny file, then the system assumes everyone has permission to use the at facility. This could create an insecure setting in the case of malicious users or system intruders.
Fix
Add appropriate users to the at.deny file, or remove the empty at.deny file if an at.allow file exists.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000590: The system must use a FIPS 140-2 approved cryptographic hashing algorithm for generating account password hashes.
Determine if the system creates password hashes using a FIPS 140-2 approved cryptographic hashing algorithm by verifying the value of pwd_algorithm in /etc/security/login.cfg. # grep pwd_algorithm /etc/security/login.cfg If the system is not configured to generate password hashes using a FIPS 140-2 approved algorithm, such as SHA256 or a successor, this is a finding.
Discussion
Systems must employ cryptographic hashes for passwords using the SHA-2 family of algorithms or FIPS 140-2 approved successors. The use of unapproved algorithms may result in weak password hashes that are more vulnerable to compromise.
Fix
Configure the system to use a FIPS 140-2 approved cryptographic hash algorithm for creating password hashes. # chsec -f /etc/security/login.cfg -s usw -a pwd_algorithm=ssha256
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003610: The system must not send IPv4 ICMP redirects.
# /usr/sbin/no -o ipsendredirects If the value is not 0, this is a finding.
Discussion
ICMP redirect messages are used by routers to inform hosts a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
Fix
#/usr/sbin/no -p -o ipsendredirects=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003600: The system must not forward IPv4 source-routed packets.
# /usr/sbin/no -o ipsrcrouteforward If the returned value is not 0, this is a finding.
Discussion
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.
Fix
# /usr/sbin/no -po "ipsrcrouteforward=0"
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005190: The .Xauthority files must not have extended ACLs.
Get a list of (non-system account) users and the associated home directories. # cat /etc/passwd | cut -f 1,6 -d ":" Check the file permissions for the user .Xauthority files. #aclget .Xauthority Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
.Xauthority files ensure the user is authorized to access that specific X Windows host. Extended ACLs may permit unauthorized modification of these files, which could lead to Denial of Service to authorized access or allow unauthorized access to be obtained.
Fix
Remove the extended ACL from the .Xauthority file(s) and disable extended permissions. #acledit .Xauthority
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001180: All network services daemon files must have mode 0755 or less permissive.
Check the mode of network services daemons. # ls -la /usr/sbin /usr/bin If the mode of a network services daemon is more permissive than 0755, this is a finding. NOTE: Network daemons that may not reside in these directories (such as httpd or sshd) must also be checked for the correct permissions.
Discussion
Restricting permission on daemons will protect them from unauthorized modification and possible system compromise.
Fix
Change the mode of the network services daemon. # chmod 0755 <path>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006480: The system must have a host-based intrusion detection tool installed.
Ask the SA or IAO if a host-based intrusion detection application is loaded on the system. Determine if the application is loaded on the system. Procedure: # find / -name <daemon name> -print Determine if the application is active on the system. Procedure: # ps -ef | grep <daemon name> If no host-based intrusion detection system is installed on the system, this is a finding.
Discussion
Without a host-based intrusion detection tool, there is no system-level defense when an intruder gains access to a system or network. Additionally, a host-based intrusion detection tool can provide methods to immediately lock out detected intrusion attempts.
Fix
Install a host-based intrusion detection tool.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003090: Crontab files must not have extended ACLs.
Check the permissions of the crontab files. Get a listing of crontab files. # ls /var/spool/cron/crontabs Check all of the crontabs listed for an extended ACL. # aclget <directory>/<file> Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
To protect the integrity of scheduled system jobs and to prevent malicious modification to these jobs, crontab files must be secured. ACLs on crontab files may provide unauthorized access to the files.
Fix
Remove the extended ACL from the crontab file(s) and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006565: The system package management tool must be used to verify system software periodically.
Check the root crontab for a job invoking the system package management tool to verify the integrity of installed packages. # crontab -l | grep lppchk If no such job exists, this is a finding.
Discussion
Verification using the system package management tool can be used to determine that system software has not been tampered with. This requirement is not applicable to systems that do not use package management tools.
Fix
Add a job to the root crontab invoking the system package management tool to verify the integrity of installed packages. # lppchk -c
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006290: The /etc/news/hosts.nntp.nolimit file must not have an extended ACL.
Check the permissions of the file. # find / -name hosts.nntp.nolimit # aclget < hosts.nntp.nolimit > If the extended permissions are enabled the file has an extended ACL, this is a finding.
Discussion
File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. Excessive permissions on the hosts.nntp.nolimit file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.
Fix
Remove the extended ACL from the hosts.nntp.nolimit file. # acledit < hosts.nntp.nolimit > Set the extended permissions to disabled.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003523: The kernel core dump data directory must not have an extended ACL.
Determine the core file copy location from the sysdumpdev command. #sysdumpdev -l | grep -I "core dir" Determine if the kernel core dump data directory has an extended ACL. #aclget < directory > Verify if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Kernel core dumps may contain the full contents of system memory at the time of the crash. As the system memory may contain sensitive information, it must be protected accordingly. If there is an extended ACL for the kernel core dump data directory, unauthorized users may be able to view or to modify kernel core dump data files.
Fix
Remove the extended ACL from the kernel core dump data directory and disable extended permissions. #acledit < directory >
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN006330: The /etc/news/passwd.nntp file must not have an extended ACL.
Check the permissions of the file. # find / -name passwd.nntp # ls -lL < passwd.nntp > If extended permissions are enabled, this is a finding.
Discussion
Extended ACLs may provide excessive permissions on the /etc/news/passwd.nntp file, which may permit unauthorized access or modification to the NNTP configuration.
Fix
Remove the extended ACL from the passwd.nntp file. # acledit < passwd.nntp >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009340: Xserver login managers must not be running unless needed for X11 session management.
Check to see if X display login managers are running. #cat /etc/inittab | grep -e /etc/rc.dt -e xdm If any X server login managers are running, ask the SA if they are necessary for the operation of the system. If there is unnecessary X server login managers running, this is a finding.
Discussion
Running Xservers and X-login managers when not needed for X11 session management increases the attack vector of the system by running unnecessary services.
Fix
Comment out or remove the X login servers from the /etc/inittab file. #vi /etc/inittab Refresh the init process. # init q
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009160: The system must not have the Calendar Manager Service Daemon (CMSD) service active.
Check the /etc/inetd.conf file for active CMSD service. # grep 'rpc\.cmsd' /etc/inetd.conf |grep -v \# If the CMSD service is enabled, this is a finding.
Discussion
The CMSD service for CDE is an unnecessary process that runs a root and increases attack vector of the system. Buffer overflow attacks against the CMSD process can potentially give access to the system.
Fix
Edit /etc/inetd.conf and comment out the CMSD service. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002660: Auditing must be implemented.
Determine if auditing is enabled. # /usr/sbin/audit query | head -1 If the response Auditing On is not returned, this is a finding.
Discussion
Without auditing, individual system accesses cannot be tracked and malicious activity cannot be detected and traced back to an individual account.
Fix
Use SMIT or command line to enable auditing on the system. #audit start Additionally, make sure auditing subsystem starts on system startup. #mkitab -i cron "audit:2:once:/usr/sbin/audit start 2>&1 > /dev/console"
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005500: The SSH daemon must be configured to only use the SSHv2 protocol.
Examine the sshd configuration file. # grep -i Protocol /etc/ssh/sshd_config If Protocol 2,1 or Protocol 1 are defined on a line without a leading comment, this is a finding.
Discussion
SSHv1 is not a DoD-approved protocol and has many well-known vulnerability exploits. Exploits of the SSH daemon could provide immediate root access to the system.
Fix
Edit the configuration file and modify the Protocol line. Protocol 2 Restart sshd: /sbin/init.d/secsh stop /sbin/init.d/secsh start
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN001390: The /etc/passwd file must not have an extended ACL.
Verify the /etc/passwd file has no extended ACL. Procedure: #aclget /etc/passwd Check to see if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
File system ACLs can provide access to files beyond what is allowed by the mode numbers of the files. The /etc/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification.
Fix
Remove the extended ACL from the /etc/passwd file and disable extended permissions. #acledit /etc/passwd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003606: The system must prevent local applications from generating source-routed packets.
# /usr/sbin/no -o ipsrcroutesend If the result is not 0, this is a finding.
Discussion
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures.
Fix
# /usr/sbin/no -po "ipsrcroutesend=0"
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003960: The traceroute command owner must be root.
# ls -lL /usr/bin/traceroute If the traceroute command is not owned by root, this is a finding.
Discussion
If the traceroute command owner has not been set to root, an unauthorized user could use this command to obtain knowledge of the network topology inside the firewall. This information may allow an attacker to determine trusted routers and other network information possibly leading to system and network compromise.
Fix
Change the owner of the traceroute command to root. Example: # chown root /usr/bin/traceroute
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003020: Cron must not execute programs in, or subordinate to, world-writable directories.
List all cronjobs on the system. Procedure: # ls /var/spool/cron/crontabs/ If cron jobs exist under any of the above directories search for programs executed by cron. Procedure: # more <cron job file> Determine if the directory containing programs executed from cron is world-writable. Procedure: # ls -ld <cron program directory> If cron executes programs in world-writable directories, this is a finding.
Discussion
If cron programs are located in or subordinate to world-writable directories, they become vulnerable to removal and replacement by malicious users or system intruders.
Fix
Remove the world-writable permission from the cron program directories identified. Procedure: # chmod o-w <cron program directory>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN999999: AIX operating systems that are no longer supported by IBM for security updates must not be installed on a system.
IBM standard support services for AIX 5.3 ended 30 April 2012. If AIX 5.3 is installed on a system and does not have an extended support services contract from IBM, this is a finding.
Discussion
AIX operating systems that are no longer supported by IBM for security updates are not evaluated or updated for vulnerabilities leaving them open to potential attack. Organizations must transition to a supported operating system to ensure continued support.
Fix
Upgrade AIX 5.3 systems to a supported operating system version or obtain an extended support services contract from IBM.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN006575: The file integrity tool must use FIPS 140-2 approved cryptographic hashes for validating file contents.
If using AIDE, verify the configuration contains the sha256 or sha512 options for all monitored files and directories. Here is an example AIDE configuration fragment. SampleRule = p+i+l+n+u+g+s+m+c+acl+xattrs+sha256 /bin SampleRule If either the sha256 or sha512 option is not present, this is a finding. If using a different file integrity tool, check the configuration per tool documentation.
Discussion
File integrity tools often use cryptographic hashes for verifying that file contents have not been altered. These hashes must be FIPS 140-2 approved.
Fix
If using AIDE, edit the configuration and add the sha256 or sha512 option for all monitored files and directories. If using a different file integrity tool, configure FIPS 140-2 approved cryptographic hashes per the tool's documentation.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001366: The /etc/hosts file must be owned by root.
Verify the /etc/hosts file is owned by root. Procedure: # ls -l /etc/hosts If the file is not owned by root, this is a finding.
Discussion
The /etc/hosts file (or equivalent) configures local host name to IP address mappings that typically take precedence over DNS resolution. If this file is maliciously modified, it could cause the failure or compromise of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.
Fix
Change the owner of the /etc/hosts file to root. # chown root /etc/hosts
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006260: The /etc/news/hosts.nntp (or equivalent) must have mode 0600 or less permissive.
Check /etc/news/hosts.nntp permissions. # find / -name hosts.nntp # ls -lL < hosts.nntp file > If /etc/news/hosts.nntp has a mode more permissive than 0600, this is a finding.
Discussion
Excessive permissions on the hosts.nntp file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.
Fix
Change the mode of the hosts.nntp file to 0600. # chmod 0600 < hosts.nntp file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX00020: AIX Trusted Computing Base (TCB) software must be implemented.
Perform: # /bin/tcbck If TCB is not installed, the output will show an error code of 3001-101 and/or a text message indicating TCB is not installed, this is a finding.
Discussion
The AIX Trusted Computing Base (TCB) software provides protection from the unauthorized modification of core system files.
Fix
Ensure the Trusted Computing Base (TCB) software is implemented. TCB can only be installed at OS installation time.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003245: The at.allow file must not have an extended ACL.
#aclget /var/adm/cron/at.allow Verify if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. Unauthorized modification of the at.allow file could result in Denial of Service to authorized at users and the granting of the ability to run at jobs to unauthorized users.
Fix
Remove the extended ACL from the at.allow file and disable extended permissions. #acledit /var/adm/cron/at.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004840: If the system is an anonymous FTP server, it must be isolated to the DMZ network.
Use the command ftp to connect the system's FTP service. Attempt to log into this host with a user name of anonymous and a password of guest (also try the password of [email protected]). If the logon is not successful, this check is not applicable. Ask the SA if the system is located on a DMZ network. If the system is not located on a DMZ network, this is a finding.
Discussion
Anonymous FTP is a public data service which is only permitted in a server capacity when located on the DMZ network.
Fix
Move the system to a DMZ network.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001700: System start-up files must only execute programs owned by a privileged UID or an application.
Check the ownership of any files executed from system startup scripts. If any of these files are not owned by root, bin, sys, or other, this is a finding.
Discussion
System start-up files executing programs owned by other than root (or another privileged user) or an application indicate the system may have been compromised.
Fix
Change the ownership of the file executed from system startup scripts to root, bin, sys, or other. # chown root <executed file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004390: The alias file must not have an extended ACL.
Check the permissions of the /etc/mail/aliases file. #aclget /etc/mail/aliases Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Excessive permissions on the aliases file may permit unauthorized modification. If the alias file is modified by an unauthorized user, they may modify the file to run malicious code or redirect e-mail.
Fix
Remove the extended ACL from the alias file and disable extended permissions. #acledit /etc/mail/aliases
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003612: The system must be configured to use TCP syncookies when experiencing a TCP SYN flood.
# /usr/sbin/no -o clean_partial_conns If the value returned is not 1, this is a finding.
Discussion
A TCP SYN flood attack can cause Denial of Service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies are a mechanism used to not track a connection until a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This technique does not operate in a fully standards-compliant manner, but is only activated when a flood condition is detected, and allows defense of the system while continuing to service valid requests.
Fix
#/usr/sbin/no -p -o clean_partial_conns=1
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003745: The inetd.conf and xinetd.conf files must not have extended ACLs.
Check the permissions of the inetd configuration file. #aclget /etc/inetd.conf Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
The Internet service daemon configuration files must be protected as malicious modification could cause Denial of Service or increase the attack surface of the system.
Fix
Remove the extended ACL from the /etc/inetd.conf file and disable extended permissions. #acledit /etc/inetd.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003460: The at.allow file must be owned by root, bin, or sys.
# ls -lL /var/adm/cron/at.allow If the at.allow file is not owned by root, sys, or bin, this is a finding.
Discussion
If the owner of the at.allow file is not set to root, bin, or sys, unauthorized users could be allowed to view or edit sensitive information contained within the file.
Fix
Change the owner of the at.allow file. # chown root /var/adm/cron/at.allow
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002690: System audit logs must be group-owned by bin, sys, or system.
Procedure: # grep -p bin: /etc/security/audit/config Directories to search will be listed under the bin stanza. # ls -la <audit directories> If any audit log file is not group-owned by bin, sys, or system, this is a finding.
Discussion
Sensitive system and user information could provide a malicious user with enough information to penetrate further into the system.
Fix
Change the group ownership of the audit log file(s). Procedure: # chgrp system < audit log file >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005440: The system must not be used as a syslog server (loghost) for systems external to the enclave.
NOTE: This will virtually always require a manual review. Ask the SA if the loghost server is collecting data for hosts outside the local enclave. If it is, this is a finding.
Discussion
Syslog messages are typically unencrypted and may contain sensitive information and are, therefore, restricted to the enclave.
Fix
Configure the hosts outside of the local enclave to not log to this system.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN007950: The system must not respond to ICMPv6 echo requests sent to a broadcast address.
# /usr/sbin/no -o bcastping If the value returned is not 0, this is a finding.
Discussion
Responding to broadcast ICMP echo requests facilitates network mapping and provides a vector for amplification attacks.
Fix
Configure the system to not respond to IPv6 multicast ICMP ECHO_REQUESTs. # /usr/sbin/no -p -o bcastping=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001392: The /etc/group file must be group-owned by security, bin, sys, or system.
Check the group ownership of the /etc/group file. Procedure: # ls -lL /etc/group If the file is not group-owned by security, bin, sys, or system, this is a finding.
Discussion
The /etc/group file is critical to system security and must be protected from unauthorized modification. The group file contains a list of system groups and associated information.
Fix
Change the group owner of the /etc/group file to security, bin, sys, or system. # chgrp security /etc/group
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005539: The SSH daemon must not allow compression or must only allow compression after successful authentication.
Check the SSH daemon configuration for the Compression setting. # grep -i Compression /etc/ssh/sshd_config | grep -v '^#' If the setting is present and set to "yes", this is a finding. If the setting is absent or set to "no" or "delayed", this is not a finding.
Discussion
If compression is allowed in an SSH connection prior to authentication, vulnerabilities in the compression software could result in compromise of the system from an unauthenticated connection, potentially with root privileges.
Fix
Edit the /etc/ssh/sshd_config file and remove the Compression setting or set the Compression setting to "delayed" or "no".
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006360: The files in /etc/news must be group-owned by system or news.
Check /etc/news files group ownership. Procedure: # ls -al /etc/news If /etc/news files are not group-owned by system or news, this is a finding.
Discussion
If critical system files do not have a privileged group owner, system integrity could be compromised.
Fix
Change the group owner of the files in /etc/news to system or news. Procedure: # chgrp news /etc/news/*
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006460: Any NIS+ server must be operating at security level 2.
If the system is not using NIS+, this is not applicable. Check the system to determine if NIS+ security level 2 is implemented. Procedure: # niscat cred.org_dir If the second column does not contain DES, the system is not using NIS+ security level 2, and this is a finding.
Discussion
If the NIS+ server is not operating in, at least, security level 2, there is no encryption and the system could be penetrated by intruders and/or malicious users.
Fix
Configure the NIS+ server to use security level 2.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006380: The system must not use UDP for NIS/NIS+.
If the system does not use NIS or NIS+, this is not applicable. Check if NIS or NIS+ is implemented using UDP. Procedure: # rpcinfo -p | grep yp | grep udp If NIS or NIS+ is implemented using UDP, this is a finding.
Discussion
Implementing NIS or NIS+ under UDP may make the system more susceptible to a Denial of Service attack and does not provide the same quality of service as TCP.
Fix
Configure the system to not use UDP for NIS and NIS+. Consult vendor documentation for the required procedure.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN005523: The SSH private host key files must have mode 0600 or less permissive.
Check the permissions for SSH private host key files. # ls -lL /etc/ssh/*key If any file has a mode more permissive than 0600, this is a finding.
Discussion
If an unauthorized user obtains the private SSH host key file, the host could be impersonated.
Fix
Change the permissions for the SSH private host key files. # chmod 0600 /etc/ssh/*key
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000240: The system clock must be synchronized to an authoritative DoD time source.
Verify if NTP running. # lssrc -s xntpd or # ps -ef | egrep "xntpd|ntpd" or # ntpq -p Verify xntpd is started at boot time and scheduled to run. #grep xntpd /etc/rc.tcpip | grep -v \# If NTP is running use the following command. # more /etc/ntp.conf and # ntpq -p Confirm the servers and peers or multicastclient (as applicable) are local or an authoritative U.S. DoD source. If a non-local/non-authoritative (U.S. DoD source) time-server is used, this is a finding.
Discussion
To assure the accuracy of the system clock, it must be synchronized with an authoritative time source within DoD. Many system functions, including time-based login and activity restrictions, automated reports, system logs, and audit records, depend on an accurate system clock. If there is no confidence in the correctness of the system clock, time-based functions may not operate as intended and records may be of diminished value. Authoritative time sources include authorized time servers within the enclave synchronizing with upstream authoritative sources. Specific requirements for the upstream synchronization of Network Time Protocol (NTP) servers are covered in the Network Other Devices STIG. For systems located on isolated or closed networks, it is not necessary to synchronize with a global authoritative time source. If a global authoritative time source is not available to systems on an isolated network, a local authoritative time source must be established on this network and used by the systems connected to this network. This is necessary to provide the ability to correlate events and allow for the correct operation of time-dependent protocols between systems on the isolated network. If the system is completely isolated (no connections to networks or other systems), time synchronization is not required as no correlation of events between systems will be necessary. If the system is completely isolated, this requirement is not applicable.
Fix
Use a local authoritative time server that synchronizes to an authorized DoD time source. Ensure all systems in the facility feed from one or more local time servers feeding from the authoritative time server. View the (x)ntp/(x)ntpd man page(s). # man xntpd Create/edit the /etc/ntp.conf file, delete any non-local and/or non-US/DoD sources and insert the local or an authoritative US/DoD source. Start or restart the NTP service. # refresh -s xntpd OR # stopsrc -s xntpd # startsrc -s xntpd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005570: The system must be configured with a default gateway for IPv6 if the system uses IPv6, unless the system is a router.
If the system is a router, this is not applicable. If the system does not use IPv6, this is not applicable. Determine if the system has a default route configured for IPv6. # netstat -r | grep default If a default route is not defined, this is a finding.
Discussion
If a system has no default gateway defined, the system is at increased risk of man-in-the-middle, monitoring, and Denial of Service attacks.
Fix
Configure an IPv6 default route on the system. # smitty route
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001660: All system start-up files must be owned by root.
Check the run control scripts' ownership. Procedure: # ls -lL /etc/rc* If any run control script is not owned by root or bin, this is a finding.
Discussion
System start-up files not owned by root could lead to system compromise by allowing malicious users or applications to modify them for unauthorized purposes. This could lead to system and network compromise.
Fix
Change the ownership of the run control script(s) with incorrect ownership. # chown root <run control script>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001940: User start-up files must not execute world-writable programs.
Check local initialization files for any executed world-writable programs or scripts. Procedure: # more /<usershomedirectory>/.* # ls -al <program or script> If any local initialization file executes a world-writable program or script, this is a finding.
Discussion
If start-up files execute world-writable programs, especially in unprotected directories, they could be maliciously modified to become Trojans destroying user files or otherwise compromising the system at the user, or higher, level. If the system is compromised at the user level, it is much easier to eventually compromise the system at the root and network level.
Fix
Remove the world-writable permission of files referenced by local initialization scripts, or remove the references to these files in the local initialization scripts.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004440: Sendmail logging must not be set to less than nine in the sendmail.cf file.
Check if Sendmail logging is set to level 9. Procedure: # grep "O L" /etc/mail/sendmail.cf OR # grep LogLevel /etc/mail/sendmail.cf If logging is set to less than 9, this is a finding.
Discussion
If Sendmail is not configured to log at level 9, system logs may not contain the information necessary for tracking unauthorized use of the Sendmail service.
Fix
Edit the sendmail.conf file, locate the "O L" or LogLevel entry and change it to 9.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001190: All network services daemon files must not have extended ACLs.
Verify network services daemon files have no extended ACLs. # aclget <directory>/<network service daemon> NOTE: Network daemons that may not reside in these directories (such as httpd or sshd) must also be checked for extended ACLs. If any of the service daemons have extended attributes enabled, this is a finding.
Discussion
Restricting permission on daemons will protect them from unauthorized modification and possible system compromise.
Fix
Remove the extended ACL(s) from the network service daemon file(s). #acledit < directory >/< network service daemon > Disable extended permissions.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002300: Device files used for backup must only be readable and/or writable by root or the backup user.
Check the system for world-writable device files. Procedure: # find / -perm -2 -a \( -type b -o -type c \) -exec ls -ld {} \; If any device file(s) used for backup are writable by users other than root, this is a finding (Typical backup devices for tape are/dev/rmt* and cd/dvd writers are /dev/cd*).
Discussion
System backups could be accidentally or maliciously overwritten and destroy the ability to recover the system if a compromise should occur. Unauthorized users could also copy system files.
Fix
Use the chmod command to remove the world-writable bit from the backup device files. Procedure: # chmod o-w <back device filename> Document all changes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003160: Cron logging must be implemented.
# ls -lL /var/adm/cron/log If this file does not exist or is older than the last cron job, this is a finding.
Discussion
Cron logging can be used to trace the successful or unsuccessful execution of cron jobs. It can also be used to spot intrusions into the use of the cron facility by unauthorized and malicious users.
Fix
Enable cron logging on the system.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001120: The system must not permit root logins using remote access programs, such as ssh.
Determine if the SSH daemon is configured to permit root logins. Procedure: # find / -name sshd_config -ls # grep -v "^#" <sshd_config path and file> | grep -i permitrootlogin If the PermitRootLogin entry is not found or is not set to no, this is a finding.
Discussion
Even though communications are encrypted, an additional layer of security may be gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account preserves the audit trail.
Fix
Edit the /etc/ssh/sshd_config file and set the PermitRootLogin option to no and refresh sshd. #kill -1 <pid of sshd>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006220: The smb.conf file must use the hosts option to restrict access to Samba.
Examine the smb.conf file. # more /usr/lib/smb.conf If the hosts option is not present to restrict access to a list of authorized hosts and networks, this is a finding.
Discussion
Samba increases the attack surface of the system and must be restricted to communicate only with systems requiring access.
Fix
Edit the smb.conf file and set the hosts option to permit only authorized hosts to access Samba.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008460: The system must have USB disabled unless needed.
AIX has server USB drivers installed, such as keyboard, mount, and mass media drivers. Determine if the system has USB enabled. # lsdev -C | grep usb # lslpp -l | grep usb If usb filesets are installed on the system, USB is enabled and this is a finding.
Discussion
USB is a common computer peripheral interface. USB devices may include storage devices that could be used to install malicious software on a system or exfiltrate data.
Fix
Disable USB devices on the system. Use SMIT to remove the following filesets. devices.usbif.* # smitty remove
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN005800: All NFS-exported system files and system directories must be owned by root.
Check for NFS exported file systems. Procedure: # exportfs -v This will display all of the exported file systems. For each file system displayed, check the ownership. Procedure: # ls -lLa <exported file system path> If the files and directories are not owned by root, this is a finding.
Discussion
Failure to give ownership of sensitive files or directories to root provides the designated owner and possible unauthorized users with the potential to access sensitive information or change system configuration which could weaken the system's security posture.
Fix
Change the ownership of exported file systems not owned by root. Procedure: # chown root <path>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004380: The alias file must have mode 0644 or less permissive.
Check the mode of the alias file. Procedure: # ls -lL /etc/mail/aliases If the alias file has a mode more permissive than 0644, this is a finding.
Discussion
Excessive permissions on the aliases file may permit unauthorized modification. If the alias file is modified by an unauthorized user, they may modify the file to run malicious code or redirect email.
Fix
Change the mode of the /etc/mail/aliases file. Procedure: # chmod 0644 /etc/mail/aliases
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002260: The system must be checked for extraneous device files at least weekly.
Check the system for an automated job, or check with the SA, to determine if the system is checked for extraneous device files on a weekly basis. If no automated or manual process is in place, this is a finding.
Discussion
If an unauthorized device is allowed to exist on the system, there is the possibility the system may perform unauthorized operations.
Fix
Establish a weekly automated or manual process to create a list of device files on the system and determine if any files have been added, moved, or deleted since the last list was generated. Generate a list of device files. # find / -type b -o -type c > device-file-list
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003602: The system must not process ICMP timestamp requests.
Determine if the system is configured to respond to ICMP Timestamp requests. #lsfilt If there is no rule blocking ICMP packet type of 13 and ICMP packet type of 14, this is a finding.
Discussion
The processing of Internet Control Message Protocol (ICMP) timestamp requests increases the attack surface of the system.
Fix
Use SMIT or genfilt commands to configure the system firewall to block ICMP packet types 13, and 14.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001900: All local initialization files' executable search paths must contain only absolute paths.
NOTE: The following must be done in the BASH shell. Examine the PATH variable contained in any user's local initialization files to ensure the use of only absolute paths, using a command shell that supports the use of ~USER as USER's home directory. # cat /etc/passwd | cut -f 1,1 -d ":" | xargs -n1 -IUSER sh -c 'grep -i PATH ~USER/.*' The PATH variable is a colon-delimited directory list. An empty entry is defined by a leading/trailing colon or two consecutive colons. A relative path is defined as an entry beginning with a character other than a slash (/). If an empty or relative path is defined in the PATH variable, this is a finding.
Discussion
The executable search path (typically the PATH environment variable) contains a list of directories for the shell to search to find executables. If this path includes the current working directory or other relative paths, executables in these directories may be executed instead of system commands. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon or two consecutive colons, this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.
Fix
Edit the local initialization file(s) and remove the relative path entry from the PATH variable.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005080: The TFTP daemon must operate in "secure mode" which provides access only to a single directory on the host file system.
If the system is not running tftp, this is not applicable. Determine if tftpd is running in secure mode. # more /etc/tftpaccess.ctl If the file does not exist, this is a finding. If the file does not contain an entry restricting access to the tftp user home directory, this is a finding. If other configuration is in the file, this is a finding.
Discussion
Secure mode limits TFTP requests to a specific directory. If TFTP is not running in secure mode, it may be able to write to any file or directory and may seriously impair system integrity, confidentiality, and availability.
Fix
Edit /etc/tftpaccess.ctl to only contain an entry restricting access to the tftp user home directory.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN003605: The system must not apply reversed source routing to TCP responses.
Determine if the system is configured to apply reverse source routing to TCP responses to source-routed packets. # /usr/sbin/no -p nonlocsrcroute If the value is not 0, this is a finding.
Discussion
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures.
Fix
Configure the system to not apply reverse source routing to TCP responses to source-routed packets. # /usr/sbin/no -po nonlocsrcroute=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001400: The /etc/security/passwd file must be owned by root.
Check the ownership of the /etc/security/passwd file. Procedure: # ls -lL /etc/security/passwd If the owner of this file is not root, this is a finding.
Discussion
The /etc/security/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.
Fix
Change the ownership of the /etc/security/passwd file. # chown root /etc/security/passwd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002280: Device files and directories must only be writable by users with a system account or as configured by the vendor.
Find all device files existing anywhere on the system. Procedure: # find / -type b -print > devicelist # find / -type c -print >> devicelist Check the permissions on the directories above subdirectories containing device files. If any of the device files or their parent directories is world-writable, excepting device files specifically intended to be world-writable, such as /dev/null, this is a finding.
Discussion
System device files in writable directories could be modified, removed, or used by an unprivileged user to control system hardware.
Fix
Remove the world-writable permission from the device file(s). Procedure: # chmod o-w <device file> Document all changes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002040: There must be no .rhosts, .shosts, hosts.equiv, or shosts.equiv files on the system.
Check for the existence of the files. # find / -name .rhosts # find / -name .shosts # find / -name hosts.equiv # find / -name shosts.equiv If .rhosts, .shosts, hosts.equiv, or shosts.equiv are found, this is a finding.
Discussion
The .rhosts, .shosts, hosts.equiv, and shosts.equiv files are used to configure host-based authentication for individual users or the system. Host-based authentication is not sufficient for preventing unauthorized access to the system.
Fix
Remove the .rhosts, .shosts, hosts.equiv, and/or shosts.equiv files.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN009230: The system must not have the echo service active.
Check the /etc/inetd.conf for TCP and UDP echo service entries. #grep echo /etc/inetd.conf | grep -v \# If the echo service is enabled, this is a finding.
Discussion
The echo service can be used in Denial of Service or SMURF attacks. It can also used at someone else to get through a firewall or start a data storm. The echo service is unnecessary and it increases the attack vector of the system.
Fix
Edit /etc/inetd.conf and comment out the echo service lines for both TCP and UDP. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002520: All public directories must be owned by root or an application account.
Check the ownership of all public directories. Procedure: # find / -type d -perm -1002 -exec ls -ld {} \; If any public directory is not owned by root or an application user, this is a finding.
Discussion
If a public directory has the sticky bit set and is not owned by a privileged UID, unauthorized users may be able to modify files created by others. The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage (e.g., /tmp) and for directories requiring global read/write access.
Fix
Change the owner of public directories to root or an application account. Procedure: # chown root /tmp (Replace root with an application user and/or /tmp with another public directory as necessary.)
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003607: The system must not accept source-routed IPv4 packets.
# /usr/sbin/no -o ipsrcrouterecv If the result is not 0, this is a finding.
Discussion
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the handling of source-routed traffic destined to the system itself, not to traffic forwarded by the system to another, such as when IPv4 forwarding is enabled and the system is functioning as a router
Fix
Configure the system to not accept source-routed IPv4 packets. #/usr/sbin/no -p -o ipsrcrouterecv=0
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000220: A file integrity tool must be used at least weekly to check for unauthorized file changes, particularly the addition of unauthorized system libraries or binaries, or for unauthorized modification to authorized system libraries or binaries.
Determine if there is a cron job, scheduled to run weekly or more frequently, to run the file integrity tool to check for unauthorized system libraries or binaries, or unauthorized modification to authorized system libraries or binaries. Procedure: # crontab -l If there is no cron job meeting these requirements, this is a finding. NOTE: For MAC I systems, increase the frequency to daily.
Discussion
Changes in system libraries and binaries can indicate compromise or significant system events, such as patching needing to be checked by automated processes and the results reviewed by the SA. NOTE: For MAC I systems, increase the frequency to daily.
Fix
Create a cron job, scheduled to run weekly or more frequently, to run the file integrity tool to check for unauthorized system libraries or binaries, or unauthorized modification to authorized system libraries or binaries. NOTE: For MAC I systems, increase the frequency to daily.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002330: Audio devices must not have extended ACLs.
Determine the audio device files for the system. Procedure: # /usr/sbin/lsdev -C | grep -i audio #aclget /dev/*aud0 Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
File system ACLs can provide access to files beyond what is allowed by the mode numbers of the files.
Fix
Remove the extended ACL from the audio device file(s) and disable extended permissions. #acledit <directory>/<file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006571: The file integrity tool must be configured to verify extended attributes.
If using AIDE, verify the configuration contains the xattrs option for all monitored files and directories. Here is an example AIDE configuration fragment. SampleRule = p+i+l+n+u+g+s+m+c+acl+xattrs+sha256 /bin SampleRule If the xattrs option is not present, this is a finding. If using a different file integrity tool, check the configuration per tool documentation.
Discussion
Extended attributes in file systems are used to contain arbitrary data and file metadata with security implications.
Fix
If using AIDE, edit the configuration and add the xattrs option for all monitored files and directories. If using a different file integrity tool, configure extended attributes checking per the tool's documentation.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003580: The system must use initial TCP sequence numbers most resistant to sequence number guessing attacks.
Check the system for the iy62006 patch. # instfix -ik iy62006 If the above patches (or successors) are not applied, this is a finding.
Discussion
One use of initial TCP sequence numbers is to verify bidirectional communication between two hosts, which provides some protection against spoofed source addresses being used by the connection originator. If the initial TCP sequence numbers for a host can be determined by an attacker, it may be possible to establish a TCP connection from a spoofed source address without bidirectional communication.
Fix
Install the iy62006 patch or its successors.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005300: SNMP communities, users, and passphrases must be changed from the default.
Check the SNMP configuration for default passwords. Locate and examine the SNMP configuration. Procedure: # find / -name "snmp*.conf" -print # more <snmpd.conf> Identify any community names or user password configuration. If any community name or password is set to a default value such as public, private, snmp-trap, or password, or any value which does not meet DISA password requirements, this is a finding.
Discussion
Whether active or not, default SNMP passwords, users, and passphrases must be changed to maintain security. If the service is running with the default authenticators, then anyone can gather data about the system and the network and use the information to potentially compromise the integrity of the system or network(s).
Fix
Change the default passwords. To change them, locate the file /etc/snmpd.conf or the file /etc/snmpd3.conf. Edit the file. Locate the line system-group-read-community which has a default password of public and make the password something more random (less guessable). Do the same for the lines that read system-group-write-community, read-community, write-community, trap, and trap-community. Read the information in the file carefully. The trap is defining who to send traps to, for instance, by default. It is not a password, but the name of a host.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN000000-AIX0300: The system must not have the bootp service active.
Check the /etc/inetd.conf file for active bootp service. # grep bootp /etc/inetd.conf |grep -v \# If the bootp service is not disabled, this is a finding.
Discussion
The bootp service is used for Network Installation Management (NIM) and remote booting of systems. The bootp service should not be active unless it is needed for NIM servers or booting remote systems. Running unnecessary services increases the attack vector of the system.
Fix
Disable the bootp service from /etc/inetd.conf. Edit /etc/inetd.conf and comment out bootp service line. Restart the inetd service. #refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002750: The audit system must be configured to audit account creation.
Determine if the audit system is configured to audit account creation. Procedure: # more /etc/security/audit/events If auditing of the USER_Create event is not configured, check the USER_Create audit event is defined in the audit classes' stanza of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config Make note of the audit class the USER_Create event is associated with. If the USER_Create event is not associated with any audit classes in the classes: stanza, this is a finding. Verify the audit class is associated with the default user and all other user ids listed in the users: stanza of the /etc/security/audit/config file. Procedure: #more /etc/security/audit/config If the class(es) the USER_Create event is not associated with the default user and all the system users in the 'users:' stanza, this is a finding.
Discussion
If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises, and damages incurred during a system compromise.
Fix
Configure the audit system to audit account creation. Edit /etc/security/audit/events and add the User_Create event to the list of audited events. Edit /etc/security/audit/config and add the USER_Create audit event to an audit class in the classes: stanza. Edit the /etc/security/audit/config and assign the audit classes with the USER_Create event to the all users listed in the users: stanza.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003840: The rexec daemon must not be running.
# grep -v "^#" /etc/inetd.conf |grep rexec If any results are returned, this is a finding.
Discussion
The rexecd process provides a typically unencrypted, host-authenticated remote access service. SSH should be used in place of this service.
Fix
Edit /etc/inetd.conf and comment out the line for the rexec service. Refresh the inetd daemon. # refresh -s inetd
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN007020: The Stream Control Transmission Protocol (SCTP) must be disabled unless required.
Check the system to determine if SCTP is installed. # lslpp -L bos.net.\* If the bos.net.sctp fileset is not listed, SCTP is not installed, and this is not a finding. If the bos.net.sctp fileset is installed, ask the SA if SCTP is required for the system. If it is not, this is a finding.
Discussion
The Stream Control Transmission Protocol (SCTP) is an IETF-standardized transport layer protocol. This protocol is not yet widely used. Binding this protocol to the network stack increases the attack surface of the host. Unprivileged local processes may be able to cause the system to dynamically load a protocol handler by opening a socket using the protocol.
Fix
If SCTP is installed and not required, unload it from the kernel and uninstall it from the system. # sctpctrl unload Use SMIT to uninstall the bos.net.sctp fileset.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003220: Cron programs must not set the umask to a value less restrictive than 077.
Determine if there are any crontabs by viewing a long listing of the directory. If there are crontabs, examine them to determine what cron jobs exist. Check for any programs specifying an umask. # ls -lL /var/spool/cron/crontabs # cat <crontab file> # grep umask <cron program> If there are no cron jobs present, this vulnerability is not applicable. If any cron job contains an umask value more permissive than 077, this is a finding.
Discussion
The umask controls the default access mode assigned to newly created files. An umask of 077 limits new files to mode 700 or less permissive. Although umask is often represented as a 4-digit octal number, the first digit representing special access modes is typically ignored or required to be 0.
Fix
Edit cron script files and modify the umask to 077.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN003100: Cron and crontab directories must have mode 0755 or less permissive.
Check the mode of the crontab directory. # ls -ld /var/spool/cron/crontabs If the mode of the crontab directory is more permissive than 0755, this is a finding.
Discussion
To protect the integrity of scheduled system jobs and to prevent malicious modification to these jobs, crontab files must be secured.
Fix
Change the mode of the crontab directory. # chmod 0755 /var/spool/cron/crontabs
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000450: The system must limit users to 10 simultaneous system logins, or a site-defined number, in accordance with operational requirements.
#grep maxulogs /etc/security/user | grep -v \* If no values are returned, or any value returned is not between 1 and 10, this is a finding.
Discussion
Limiting simultaneous user logins can insulate the system from Denial of Service problems caused by excessive logins. Automated login processes operating improperly or maliciously may result in an exceptional number of simultaneous login sessions. If the defined value of 10 logins does not meet operational requirements, the site may define the permitted number of simultaneous login sessions based on operational requirements. This limit is for the number of simultaneous login sessions for EACH user account. This is NOT a limit on the total number of simultaneous login sessions on the system.
Fix
Configure the system to limit the number of simultaneous logins for user accounts with the chsec command. # chsec -f /etc/security/user -s default -a maxulogs=10 # chsec -f /etc/security/user –s [user] -a maxulogs=10
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN000930: The root account's home directory must not have an extended ACL.
Verify the root account's home directory has no extended ACL. Procedure: # aclget ~root If extended permissions are enabled, the directory has an extended ACL, and this is a finding.
Discussion
File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files.
Fix
Remove the extended ACL from the root account's home directory. #acledit ~root Change extended attributes to disabled.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX00040: The securetcpip command must be used.
The securetcpip command is in /etc. If it is not there, this is a finding. Perform: more /etc/security/config If the stanza below is not there, this is a finding. tcpip: netrc = ftp, rexec The stanza indicates the securetcpip command, which disables all the unsafe tcpip commands, (e.g., rsh, rlogin, tftp) has been executed.
Discussion
The AIX securetcpip command disables insecure network utilities, such as rcp, rlogin, rlogind, rsh, rshd, tftp, tftpd, and trpt/d. These services increase the attack surface of the system.
Fix
Ensure secure tcp/ip has been invoked before allowing operations on the system.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003815: The portmap or rpcbind service must not be installed unless needed.
If the system needs the portmap service to operate, this is not applicable. Consult vendor documentation to determine the name and location of the portmap service. The portmap executable is part of fileset bos.net.tcp.client and is not removable, so this will always be a finding.
Discussion
The portmap and rpcbind services increase the attack surface of the system and should only be used when needed. The portmap or rpcbind services are used by a variety of services using Remote Procedure Calls (RPCs).
Fix
If the portmap or rpcbind service is part of a removable package, consult vendor documentation for the procedure to remove the package. If the service cannot be removed, prevent service activation by removing all permissions from the executable. Procedure: # chmod 0000 /usr/sbin/portmap
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003950: The hosts.lpd (or equivalent) file must not have an extended ACL.
Check the permissions of the /etc/hosts.lpd file. #aclget /etc/hosts.lpd Check if extended permissions are disabled. If extended permissions are not disabled, this is a finding.
Discussion
Excessive permissions on the hosts.lpd (or equivalent) file may permit unauthorized modification. Unauthorized modifications could disrupt access to local printers from authorized remote hosts or permit unauthorized remote access to local printers.
Fix
Remove the extended ACL from the hosts.lpd file and disable extended permissions. #acledit /etc/hosts.lpd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0310: The /etc/ftpaccess.ctl file must exist.
Check for the existence of the /etc/ftpaccess.ctl file. # ls -l /etc/ftpaccess.ctl If the ftpaccess.ctl file does not exist, this is a finding.
Discussion
The ftpaccess.ctl file contains options for the ftp daemon, such as herald, motd, user access, and permissions to files and directories. If the ftpaccess.ctl file does not exist, the ftpd process will not display any warning banners, and permissions will only be enforced using basic UNIX permissions.
Fix
Create a /etc/ftpaccess.ctl file. #touch /etc/ftpaccess.ctl Add at least the herald: /path to login banner to the /etc/ftpaccess.ctl file. #vi /etc/ftpaccess.ctl
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009270: The system must not have the netstat service active on the inetd process.
Check the /etc/inetd.conf for active netstat service. grep netstat /etc/inetd.conf | grep -v \# If the netstat service is active, this is a finding.
Discussion
The netstat service can potentially give out network information on active connections if it is running. The information given out can aid in an attack and weaken the systems defensive posture.
Fix
Edit /etc/inetd.conf and comment out the netstat service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN006320: The /etc/news/passwd.nntp file (or equivalent) must have mode 0600 or less permissive.
Check /etc/news/passwd.nntp permissions. # find / -name passwd.nntp # ls -lL < passwd.nntp > If passwd.nntp has a mode more permissive than 0600, this is a finding.
Discussion
File permissions more permissive than 0600 for /etc/news/passwd.nntp may allow access to privileged information by system intruders or malicious users.
Fix
Change the mode of the passwd.nntp file. # chmod 0600 < passwd.nntp >
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002500: The sticky bit must be set on all public directories.
Verify all world-writable directories have the sticky bit set. Procedure: # find / -type d -perm -002 ! -perm -1000 > wwlist If the sticky bit is not set on a world-writable directory, this is a finding.
Discussion
Failing to set the sticky bit on the public directories allows unauthorized users to delete files in the directory structure. The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage (e.g., /tmp) and for directories requiring global read/write access.
Fix
Set the sticky bit on all public directories. Procedure: # chmod 1777 /tmp (Replace /tmp with the public directory missing the sticky bit, if necessary.)
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
GEN001000: Remote consoles must be disabled or protected from unauthorized access.
Check /etc/security/login.cfg # more /etc/security/login.cfg If an alternate console is defined, this is a finding.
Discussion
The remote console feature provides an additional means of access to the system which could allow unauthorized access if not disabled or properly secured. With virtualization technologies, remote console access is essential as there is no physical console for virtual machines. Remote console access must be protected in the same manner as any other remote privileged access method.
Fix
Edit /etc/security/login.cfg and remove the alternate console definition.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000100: The operating system must be a supported release.
# oslevel Vendor supported versions are 5.3 and later at the time of writing. AIX 5.3 End of support 30 April 2012 AIX 5.2 End of support 30 April 2009 AIX 5.1 End of support 1 April 2006 If the release is not supported, this is a finding.
Discussion
An operating system release is considered "supported" if the vendor continues to provide security patches for the product. With an unsupported release, it will not be possible to resolve security issues discovered in the system software.
Fix
Upgrade to a supported version of the operating system.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN000000-AIX0085: The /etc/netsvc.conf file must be root owned.
Verify the /etc/netsvc.conf file is owned by root. # ls -l /etc/netsvc.conf If the file is not owned by root, this is a finding.
Discussion
The /etc/netsvc.conf file is used to specify the ordering of name resolution for the sendmail command, alias resolution for the sendmail command, and host name resolution routines. Malicious changes could prevent the system from functioning correctly or compromise system security.
Fix
Change the owner of the /etc/netsvc.conf file to root. # chown root /etc/netsvc.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005540: The SSH daemon must be configured for IP filtering.
Check the TCP wrappers configuration files to determine if SSHD is configured to use TCP wrappers. Procedure: # grep sshd /etc/hosts.deny # grep sshd /etc/hosts.allow If no entries are returned, the TCP wrappers are not configured for SSHD and this is a finding.
Discussion
The SSH daemon must be configured for IP filtering to provide a layered defense against connection attempts from unauthorized addresses.
Fix
Add appropriate IP restrictions for SSH to the /etc/hosts.deny and/or /etc/hosts.allow files. TCP Wrappers can be installed using SMIT from the AIX expansion pack as fileset netsec.options.tcpwrappers.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004500: The SMTP service log file must have mode 0644 or less permissive.
Check the mode of the SMTP service log file. Procedure: # more /etc/syslog.conf Check the configuration to determine which log files contain logs for mail.crit, mail.debug, or *.crit. Procedure: # ls -lL <file location> If the log file permissions are greater than 0644, this is a finding.
Discussion
If the SMTP service log file is more permissive than 0644, unauthorized users may be allowed to change the log file.
Fix
Change the mode of the SMTP service log file. Procedure: # chmod 0644 <sendmail log file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0100: The /etc/netsvc.conf file must have mode 0644 or less permissive.
Check the mode of the /etc/netsvc.conf file. # ls -l /etc/netsvc.conf If the file mode is more permissive than 0644, this is a finding.
Discussion
The /etc/netsvc.conf file is used to specify the ordering of name resolution for the sendmail command, alias resolution for the sendmail command, and host name resolution routines. Malicious changes could prevent the system from functioning correctly or compromise system security.
Fix
Change the mode of the /etc/netsvc.conf file to 0644 or less permissive. # chmod 0644 /etc/netsvc.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001580: All run control scripts must have mode 0755 or less permissive.
Check run control script modes. # cd /etc # find rc* -ls If any run control script has a mode more permissive than 0755, this is a finding.
Discussion
If the startup files are writable by other users, they could modify the startup files to insert malicious commands into the startup files.
Fix
Ensure all system startup files have mode 0755 or less permissive. Examine the rc files, all files in the rc1.d (rc2.d, and so on) directories, and in the /etc/init.d directory to ensure they are not world-writable. If the files are world-writable, use the chmod command to correct the vulnerability and research why they are world-writable. Procedure: # chmod 755 startupfile Document all changes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000500: Graphical desktop environments provided by the system must automatically lock after 15 minutes of inactivity and the system must require users to re-authenticate to unlock the environment.
Log into a graphical desktop environment provided by the system. Allow the session to remain idle for 15 minutes. If the desktop session is not automatically locked after 15 minutes, or does not require re-authentication to resume operations, this is a finding.
Discussion
If graphical desktop sessions do not lock the session after 15 minutes of inactivity, requiring re-authentication to resume operations, the system or individual data could be compromised by an alert intruder who could exploit the oversight. This requirement applies to graphical desktop environments provided by the system to locally attached displays and input devices, as well as, to graphical desktop environments provided to remote systems, including thin clients.
Fix
Consult vendor documentation to determine the settings required for the system to lock graphical desktop environments. Configure the system to lock graphical desktop environments after 15 minutes of inactivity and require re-authentication to resume operations.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000945: The root account's library search path must be the system default and must contain only absolute paths.
Verify the LIBPATH and LD_LIBRARY_PATH variables are empty or not defined for the root user. # echo $LD_LIBRARY_PATH # echo $LIBPATH If a path list is returned, this is a finding.
Discussion
The library search path environment variable(s) contains a list of directories for the dynamic linker to search to find libraries. If this path includes the current working directory or other relative paths, libraries in these directories may be loaded instead of system libraries. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon or two consecutive colons, this is interpreted as the current working directory. Entries starting with a slash (/) are absolute paths.
Fix
Edit the root user's initialization files and remove any definition of LD_LIBRARY_PATH and LIBPATH.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN005395: The /etc/syslog.conf file must not have an extended ACL.
Check the permissions of the syslog configuration file. # aclget /etc/syslog.conf If the extended attributes are not disabled, this is a finding
Discussion
Unauthorized users must not be allowed to access or modify the /etc/syslog.conf file.
Fix
Remove the extended ACL from the syslog.conf file and change extended attributes to disabled. #acledit /etc/syslog.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX00080: The SYSTEM attribute must not be set to NONE for any account.
Examine the /etc/security/user file. # grep SYSTEM /etc/security/user If the line contains SYSTEM=NONE, this is a finding.
Discussion
The SYSTEM attribute in /etc/security/user defines the mechanisms used to authenticate specific user accounts. If the value is set to NONE, other attributes will be used to determine the authentication mechanisms, but if these attributes are not present, no authentication will be performed. To ensure authentication is always used for the system's accounts, the SYSTEM attribute must always be set to a valid setting other than NONE.
Fix
Edit /etc/security/user and change any SYSTEM=NONE settings to a valid authentication setting.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN005750: The NFS export configuration file must be group-owned by root, bin, sys, or system.
Check the group ownership of the NFS export configuration file. Procedure: # ls -lL /etc/exports If the file is not group-owned by root, bin, sys, or system, this is a finding.
Discussion
Failure to give group ownership of the NFS export configuration file to root or a system group provides the designated group owner and possible unauthorized users with the potential to change system configuration which could weaken the system's security posture.
Fix
Change the group ownership of the NFS export configuration file to root, bin, sys, or system. Procedure: # chgrp root /etc/exports
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000960: The root account must not have world-writable directories in its executable search path.
Check for world-writable permissions on all directories in the root user's executable search path. Procedure: # ls -ld `echo $PATH | sed "s/:/ /g"` If any of the directories in the PATH variable are world-writable, this is a finding.
Discussion
If the root search path contains a world-writable directory, malicious software could be placed in the path by intruders and/or malicious users and inadvertently run by root with all of root's privileges.
Fix
For each world-writable path in root's executable search path, perform one of the following. 1. Remove the world-writable permission on the directory. Procedure: # chmod o-w <path> 2. Remove the world-writable directory from the executable search path. Procedure: Identify and edit the initialization file referencing the world-writable directory and remove it from the PATH variable.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008380: A root kit check tool must be run on the system at least weekly.
Ask the SA if a root kit check tool is run on the system weekly. If this is not performed, this is a finding.
Discussion
Root kits are software packages designed to conceal the compromise of a system from the SA. Root kit checking tools examine a system for evidence that a root kit is installed. Dedicated root kit detection software or root kit detection capabilities included in anti-virus packages may be used to satisfy this requirement.
Fix
Create an automated job or establish a site-defined procedure to check the system weekly with a root kit check tool.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008640: The system must not use removable media as the boot loader.
Check the servers boot lists for the normal, service, both, or prevboot modes. # bootlist -m <mode> -o Ensure hdisk{x} is the only devices listed. If boot devices, such as cd{x}, fd{x}. rmt{x}, ent{x} are used, this is a finding.
Discussion
Malicious users with removable boot media can gain access to a system configured to use removable media as the boot loader.
Fix
Configure the system to use a bootloader installed on fixed media. # bootlist -m normal hdisk0 # bootlist -m service hdisk0
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
GEN000585: The system must enforce the entire password during authentication.
Verify no password hashes in /etc/passwd. # cat /etc/passwd | cut -f2,2 -d":" If there are password hashes present, this is a finding. Verify no password hashes in the /etc/security/passwd file begin with the characters other than {ssha256} or {ssha512} #cat /etc/security/passwd | grep password If there are password hashes that do not begin with {ssha256} or {ssha512}, this is a finding.
Discussion
Some common password hashing schemes only process the first eight characters of a user's password, which reduces the effective strength of the password.
Fix
Configure the system to enforce the correctness of the entire password during authentication. Configure the system to use sha password hashing. #chsec -f /etc/security/login.cfg -s usw -a pwd_algorithm=ssha256
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002020: All .rhosts, .shosts, or host.equiv files must only contain trusted host-user pairs.
Locate and examine all .rhosts, .shosts, hosts.equiv, and shosts.equiv files. Procedure: # find / -name .rhosts # more /<directorylocation>/.rhosts # find / -name .shosts # more /<directorylocation>/.shosts # find / -name hosts.equiv # more /<directorylocation>/hosts.equiv # find / -name shosts.equiv # more /<directorylocation>/shosts.equiv If any .rhosts, .shosts, hosts.equiv, or shosts.equiv file contains other than host-user pairs, this is a finding.
Discussion
If these files are not properly configured, they could allow malicious access by unknown malicious users from untrusted hosts who could compromise the system.
Fix
If possible, remove the .rhosts, .shosts, hosts.equiv, and shosts.equiv files. If the files are required, remove any content from the files except for necessary host-user pairs.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003940: The hosts.lpd (or equivalent) must have mode 0644 or less permissive.
Locate any print service configuration file on the system. Consult vendor documentation for the name and location of print service configuration files. Procedure: # find /etc -name hosts.lpd -print # find /etc -name Systems -print If no print service configuration file is found, this is not applicable. Check the mode of the print service configuration file. Procedure: # ls -lL <print service file> If the mode of the print service configuration file is more permissive than 0644, this is a finding.
Discussion
Excessive permissions on the hosts.lpd (or equivalent) file may permit unauthorized modification. Unauthorized modifications could disrupt access to local printers from authorized remote hosts or permit unauthorized remote access to local printers.
Fix
Change the mode of the /etc/hosts.lpd file (or equivalent, such as /etc/lp/Systems) to 0644 or less permissive. Consult vendor documentation for the name and location of print service configuration files. Procedure: # chmod 0644 /etc/hosts.lpd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008100: If the system is using LDAP for authentication or account information, the /etc/ldap.conf (or equivalent) file must be group-owned by security, bin, sys, or system.
Check the group ownership of the ldap.cfg file. Procedure: # ls -lL /etc/security/ldap/ldap.cfg If the file is not group-owned by bin, security, sys, or system, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Change the group owner of the /etc/security/ldap/ldap.cfg file to security, bin, sys, or system. Procedure: # chgrp security /etc/security/ldap/ldap.cfg
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN009330: The system must not have the rstatd service active.
Check the /etc/inetd.conf file for active rstatd service. #grep rstatd /etc/inetd.conf | grep -v \# If the rstatd service is enabled, this is a finding.
Discussion
The rstatd can give out information on the running system, such as the CPU usage, the system uptime, its network usage, and other system information that could potentially aid in an attack. The rstatd service is unnecessary and it weakens the defensive posture of the system. If systems monitoring is needed, use a third party tool or SNMP.
Fix
Edit the /etc/inetd.conf file and comment out the rstatd service line. Restart the inetd service. # refresh -s inetd
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN008080: If the system is using LDAP for authentication or account information, the /etc/ldap.conf (or equivalent) file must be owned by root.
Check the ownership of the /etc/security/ldap/ldap.cfg file. # ls -lL /etc/security/ldap/ldap.cfg If the file is not owned by root, this is a finding.
Discussion
LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.
Fix
Change the owner of the /etc/security/ldap/ldap.cfg file. # chown root /etc/security/ldap/ldap.cfg
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN002680: System audit logs must be owned by root.
Perform the following to determine the location of audit logs and then check the ownership. Procedure: # grep -p bin: /etc/security/audit/config Directories to search will be listed under the bin stanza. # ls -la <audit directories> If any audit log file is not owned by root, this is a finding.
Discussion
Failure to give ownership of system audit log files to root provides the designated owner and unauthorized users with the potential to access sensitive information.
Fix
Change the ownership of the audit log file(s). Procedure: # chown root <audit log file>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN003810: The portmap or rpcbind service must not be running unless needed.
If the portmap service is required for system operations, this is not a finding. Determine if the portmap service is running. #ps -ef|grep portmap If portmap is running, this is a finding.
Discussion
The portmap and rpcbind services increase the attack surface of the system and should only be used when needed. The portmap or rpcbind services are used by a variety of services using Remote Procedure Calls (RPCs).
Fix
Disable the portmap service from auto starting by commenting out portmap from /etc/rc.tcpip. # vi /etc/rc.tcpip Shutdown the portmap service. # ps -ef | grep portmap # kill <pid of portmap>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN001365: The /etc/resolv.conf file must not have an extended ACL.
Verify /etc/resolv.conf has no extended ACL. Check if extended permissions are disabled. Procedure: #aclget /etc/resolv.conf If extended permissions are not disabled, this is a finding.
Discussion
The resolv.conf (or equivalent) file configures the system's DNS resolver. DNS is used to resolve host names to IP addresses. If DNS configuration is modified maliciously, host name resolution may fail or return incorrect information. DNS may be used by a variety of system security functions such as time synchronization, centralized authentication, and remote system logging.
Fix
Remove the extended ACL from /etc/resolv.conf file and disable extended permissions. #acledit /etc/resolv.conf
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN000000-AIX0330: The /etc/ftpaccess.ctl file must be group-owned by bin, sys, or system.
Check the group ownership of the ftpaccess.ctl file. # ls -lL /etc/ftpaccess.ctl If the /etc/ftpaccess.ctl file is not group-owned by bin, sys, or system, this is a finding.
Discussion
If the ftpaccess.ctl file is not group-owned by a system group, an unauthorized user may modify the file to allow unauthorized access to modify the file. Unauthorized modification could result in Denial of Service to authorized FTP users or permit unauthorized access to system information.
Fix
Change the group owner of the /etc/ftpaccess.ctl file. # chgrp system /etc/ftpaccess.ctl
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
GEN004710: Mail relaying must be restricted.
If the system uses Sendmail, locate the sendmail.cf file. Procedure: # find / -name sendmail.cf Determine if Sendmail only binds to loopback addresses by examining the DaemonPortOptions configuration options. Procedure: # grep -i "O DaemonPortOptions" /etc/mail/sendmail.cf If there are uncommented DaemonPortOptions lines, and all such lines specify system loopback addresses, this is not a finding. Otherwise, determine if Sendmail is configured to allow open relay operation. Procedure: # find / -name sendmail.mc # grep -i promiscuous_relay </path/to/sendmail.mc> If the promiscuous relay feature is enabled, this is a finding. If the system uses Postfix, locate the main.cf file. Procedure: # find / -name main.cf Determine if Postfix only binds to loopback addresses by examining the inet_interfaces line. Procedure: # grep inet_interfaces </path/to/main.cf> If inet_interfaces is set to loopback-only or contains only loopback addresses such as 127.0.0.1 and [::1], Postfix is not listening on external network interfaces, and this is not a finding. Otherwise, determine if Postfix is configured to restrict clients permitted to relay mail by examining the smtpd_client_restrictions line. Procedure: # grep smtpd_client_restrictions </path/to/main.cf> If the smtpd_client_restrictions line is missing, or does not contain reject, this is a finding. If the line contains permit before reject, this is a finding. If the system is using other SMTP software, consult the software's documentation for procedures to verify that mail relaying is restricted.
Discussion
If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay for the purpose of sending SPAM or other unauthorized activity.
Fix
If the system uses Sendmail, edit the sendmail.mc file and remove the promiscuous_relay configuration. Rebuild the sendmail.cf file from the modified sendmail.mc and restart the service. If the system does not need to receive mail from external hosts, add one or more DaemonPortOptions lines referencing system loopback addresses (such as "O DaemonPortOptions=Addr=127.0.0.1, Port=smtp, Name=MTA") and remove lines containing non-loopback addresses. Restart the service. If the system uses Postfix, edit the main.cf file and add or edit the smtpd_client_restrictions line to have contents permit mynetworks, reject or a similarly restrictive rule. If the system does not need to receive mail from external hosts, add or edit the inet_interfaces line to have contents loopback-only or a set of loopback addresses for the system. Restart the service. If the system is using other SMTP software, consult the software's documentation for procedures to restrict mail relaying.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None