Monitor changes to file permissions, attributes, ownership and group. The parameters in this section track changes for system calls that affect file permissions and attributes. The chmod, fchmod and fchmodat system calls affect the permissions associated with a file. The chown, fchown, fchownat and lchown system calls affect owner and group attributes on a file. The setxattr, lsetxattr, fsetxattr (set extended file attributes) and removexattr, lremovexattr, fremovexattr (remove extended file attributes) control extended file attributes. In all cases, an audit record will only be written for non-system userids (auid >= 500) and will ignore Daemon events (auid = 4294967295). All audit records will be tagged with the identifier perm_mod. Rationale: Monitoring for changes in file attributes could alert a system administrator to activity that could indicate intruder activity or policy violation. Fix: For 64 bit systems, add the following lines to the /etc/audit/audit.rules file. -a always,exit -F arch=b64 -S chmod -S fchmod -S fchmodat -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S chmod -S fchmod -S fchmodat -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b64 -S chown -S fchown -S fchownat -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S chown -S fchown -S fchownat -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b64 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod # Execute the following command to restart auditd # pkill -HUP -P 1 auditd For 32 bit systems, add the following lines to the /etc/audit/audit.rules file. -a always,exit -F arch=b32 -S chmod -S fchmod -S fchmodat -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S chown -S fchown -S fchownat -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod # Execute the following command to restart auditd # pkill -HUP -P 1 auditd

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For 64 bit systems, add the following lines to the /etc/audit/audit.rules file. -a always,exit -F arch=b64 -S chmod -S fchmod -S fchmodat -F auid =500 \ -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S chmod -S fchmod -S fchmodat -F auid =500 \ -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b64 -S chown -S fchown -S fchownat -S lchown -F auid =500 \ -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S chown -S fchown -S fchownat -S lchown -F auid =500 \ -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b64 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S \ lremovexattr -S fremovexattr -F auid =500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S \ lremovexattr -S fremovexattr -F auid =500 -F auid!=4294967295 -k perm_mod # Execute the following command to restart auditd # pkill -HUP -P 1 auditd For 32 bit systems, add the following lines to the /etc/audit/audit.rules file. -a always,exit -F arch=b32 -S chmod -S fchmod -S fchmodat -F auid =500 \ -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S chown -S fchown -S fchownat -S lchown -F auid =500 \ -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S \ lremovexattr -S fremovexattr -F auid =500 -F auid!=4294967295 -k perm_mod # Execute the following command to restart auditd # pkill -HUP -P 1 auditd