Title

IBM z/OS UNIX security parameters for restricted network service(s) in /etc/inetd.conf must be properly specified. (Cat II impact)

Discussion

In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports/protocols on information systems. Operating systems are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., VPN and IPS); however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the operating system must support the organizational requirements, providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues.

Check Content

From the UNIX System Services ISPF Shell enter: /etc/inetd.conf If any Restricted Network Services that are listed below are specified or specified but not commented out, this is a finding. RESTRICTED NETWORK SERVICES/PORTS Service Port Chargen 19 Daytime 13 Discard 9 Echo 7 Exec 512 finger 79 shell 514 time 37 login 513 smtp 25 timed 525 nameserver 42 systat 11 uucp 540 netstat 15 talk 517 qotd 17 tftp 69

Fix Text

Review the settings in the /etc/inetd.conf file determine if every entry in the file represents a service that is actually in use. Services that are not in use must be disabled to reduce potential security exposures. The following services must be disabled in /etc/inetd.conf unless justified and documented with the ISSO: RESTRICTED NETWORK SERVICES Service Port Chargen 19 Daytime 13 Discard 9 Echo 7 Exec 512 finger 79 shell 514 time 37 login 513 smtp 25 timed 525 nameserver 42 systat 11 uucp 540 netstat 15 talk 517 qotd 17 tftp 69 The /etc/inetd.conf file is used by the INETD daemon. It specifies how INETD is to handle service requests on network sockets. Specifically, there is one entry in inetd.conf for each service. Each service entry specifies several parameters. The login_name parameter is of special interest. It specifies the userid under which the forked daemon is to execute. This userid is defined to the ACP and it may require a UID(0) (i.e., superuser authority) value.

Additional Identifiers

Rule ID: SV-223855r604139_rule

Vulnerability ID: V-223855

Group Title: SRG-OS-000096-GPOS-00050

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.