InformationRecord events affecting the modification of user or group information, including that of passwords and old passwords if in use.
/etc/group - system groups
/etc/passwd - system users
/etc/gshadow - encrypted password for each group
/etc/shadow - system user passwords
/etc/security/opasswd - storage of old passwords if the relevant PAM module is in use
The parameters in this section will watch the files to see if they have been opened for write or have had attribute changes (e.g. permissions) and tag them with the identifier 'identity' in the audit log file.
Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts.
SolutionEdit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information.
# printf '
-w /etc/group -p wa -k identity
-w /etc/passwd -p wa -k identity
-w /etc/gshadow -p wa -k identity
-w /etc/shadow -p wa -k identity
-w /etc/security/opasswd -p wa -k identity
' >> /etc/audit/rules.d/50-identity.rules
Merge and load the rules into active configuration:
# augenrules --load
Check if reboot is required.
# if [[ $(auditctl -s | grep 'enabled') =~ '2' ]]; then printf 'Reboot required to load rules
Potential reboot required
If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration.
System call structure
For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page.