Detections
Analytics

6.2.3.22 Ensure file deletion events by users are collected

Information

Monitor the use of system calls associated with the deletion or renaming of files and file attributes. This configuration statement sets up monitoring for:

 - unlink - removes a file
 - unlinkat - removes a file or empty directory at a path relative to a directory file descriptor
 - rename - renames a file
 - renameat - renames a file or directory at a path relative to a directory file descriptor and tags them with the identifier "delete".
 - renameat2 - system call operates in exactly the same way as renameat with some minor differences

Monitoring these calls from non-privileged users could provide a system administrator with evidence that inappropriate removal of files and file attributes associated with protected files is occurring. While this audit option will look at all events, system administrators will want to look for specific privileged files that are being deleted or altered.

Solution

Create audit rules

Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor file deletion events by users.

Example:

# {
UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)
[ -n "${UID_MIN}" ] && printf "
-a always,exit -F arch=b64 -S rename,unlink,unlinkat,renameat,renameat2 -F auid>=${UID_MIN} -F auid!=unset -F key=delete
-a always,exit -F arch=b32 -S rename,unlink,unlinkat,renameat,renameat2 -F auid>=${UID_MIN} -F auid!=unset -F key=delete
" >> /etc/audit/rules.d/50-delete.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n"
}

Load audit 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\n"; fi

See Also

https://workbench.cisecurity.org/benchmarks/26891

Item Details

Category: AUDIT AND ACCOUNTABILITY, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|AU-3, 800-53|AU-3(1), 800-53|AU-7, 800-53|AU-12, 800-53|SC-7, CSCv7|6.2, Rule-ID|SV-238310r991577_rule, Rule-ID|SV-260639r991577_rule

Plugin: Unix

Control ID: 5f3020da2611da1edeb6b6394e09c2f1b1114f3dfb324494e3c223fc7a63ca32