Title

AIX must require the change of at least 50% of the total number of characters when passwords are changed. (Cat I impact)

Discussion

If the operating system allows the user to consecutively reuse extensive portions of passwords, this increases the chances of password compromise by increasing the window of opportunity for attempts at guessing and brute-force attacks. The number of changed characters refers to the number of changes required with respect to the total number of positions in the current password. In other words, characters may be the same within the two passwords; however, the positions of the like characters must be different. If the password length is an odd number then number of changed characters must be rounded up. For example, a password length of 15 characters must require the change of at least 8 characters.

Check Content

From the command prompt, run the following command to check the system default "mindiff" attribute value: # lssec -f /etc/security/user -s default -a mindiff default mindiff=8 If the default "mindiff" value is not set, or its value is less than "8", this is a finding. From the command prompt, run the following command to check "mindiff" attribute value for all accounts: # lsuser -a mindiff ALL root mindiff=9 user1 mindiff=8 user2 mindiff=8 user3 mindiff=10 If any user's "mindiff" value is less than "8", this is a finding.

Fix Text

From the command prompt, run the following command to set "mindiff=8" (assume that the password is at least 15-character long) for the default stanza in "/etc/security/user": # chsec -f /etc/security/user -s default -a mindiff=8 For each user who has "mindiff" value less than "8", set its "mindiff" value to "8" by running the following command from command prompt: # chsec -f /etc/security/user -s [user_name] -a mindiff=8

Additional Identifiers

Rule ID: SV-215220r508663_rule

Vulnerability ID: V-215220

Group Title: SRG-OS-000072-GPOS-00040

Expert Comments

CCIs tied to check.

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