cis-ubuntu2004-v300-6-3-3-9

name	cis-ubuntu2004-v300-6-3-3-9
description	Ensure discretionary access control permission modification events are collected
category	cis-logging
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","auditing","auditd"]
cis_id	6.3.3.9
cis_benchmark	CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

6.3.3.9 Ensure discretionary access control permission modification events are collected (Automated)

Profile

• Level 2 - Server
• Level 2 - Workstation

Description

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 following commands and system calls effect the permissions, ownership and various attributes of files.

• chmod
• fchmod
• fchmodat
• chown
• fchown
• fchownat
• lchown
• setxattr
• lsetxattr
• fsetxattr
• removexattr
• lremovexattr
• fremovexattr

In all cases, an audit record will only be written for non-system user ids and will ignore Daemon events. 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.

Audit Procedure

Command Line

Note: Output showing all audited syscalls, e.g. (-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod) is also acceptable. These have been separated by function on the displayed output for clarity.

On disk configuration - Run the following command to check the on disk rules:

# {
UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)
[ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \
&&/ -F *arch=b(32|64)/ \
&&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \
&&/ -S/ \
&&/ -F *auid>=${UID_MIN}/ \
&&(/chmod/||/fchmod/||/fchmodat/ \
  ||/chown/||/fchown/||/fchownat/||/lchown/ \
  ||/setxattr/||/lsetxattr/||/fsetxattr/ \
  ||/removexattr/||/lremovexattr/||/fremovexattr/) \
&&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \
|| printf 
}