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Record Successful Permission Changes to Files - fchmodat

An XCCDF Rule

Description

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d: 

-a always,exit -F arch=b32 -S fchmodat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-perm-change
If the system is 64 bit then also add the following lines: 
-a always,exit -F arch=b64 -S fchmodat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-perm-change
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file: 
-a always,exit -F arch=b32 -S fchmodat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-perm-change
If the system is 64 bit then also add the following lines: 
-a always,exit -F arch=b64 -S fchmodat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-perm-change

warning alert: Warning

Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.

Rationale

File permission changes could be an indicator of malicious activity on a system. Auditing these events could serve as evidence of potential system compromise.

ID
xccdf_org.ssgproject.content_rule_audit_rules_successful_file_modification_fchmodat
Severity
Medium
References
Updated