cis-ubuntu1604-v200-4-1-12

name	cis-ubuntu1604-v200-4-1-12
description	Ensure successful file system mounts are collected
category	cis-logging
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","auditd","logging"]
cis_id	4.1.12
cis_benchmark	CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 4.1.12

Profile

• Level: 2 - Server
• Level: 2 - Workstation
• Assessment Status: Automated

Description

Monitor the use of the mount system call. The mount (and umount) system call controls the mounting and unmounting of file systems. The parameters below configure the system to create an audit record when the mount system call is used by a non-privileged user.

Note:

• This tracks successful and unsuccessful mount commands. File system mounts do not have to come from external media and this action still does not verify write (e.g. CD ROMS).
• Reloading the auditd config to set active settings requires the auditd service to be restarted, and may require a system reboot.

Rationale

It is highly unusual for a non privileged user to mount file systems to the system. While tracking mount commands gives the system administrator evidence that external media may have been mounted (based on a review of the source of the mount and confirming it's an external media type), it does not conclusively indicate that data was exported to the media. System administrators who wish to determine if data were exported, would also have to track successful open, creat and truncate system calls requiring write access to a file under the mount point of the external media file system. This could give a fair indication that a write occurred. The only way to truly prove it, would be to track successful writes to the external media. Tracking write system calls could quickly fill up the audit log and is not recommended. Recommendations on configuration options to track data export to media is beyond the scope of this document.

Impact

None.

Audit Procedure

Command Line

On a 32 bit system:

Run the following command to verify the rules are contained in a .rules file in the /etc/audit/rules.d/ directory:

grep mounts /etc/audit/rules.d/*.rules

Verify output matches:

-a always,exit -F arch=b32 -S mount -F auid>=1000 -F auid!=4294967295 -k mounts

Run the following command to verify that rules are in the running auditd config:

auditctl -l | grep mounts

Verify output matches:

-a always,exit -F arch=b32 -S mount -F auid>=1000 -F auid!=-1 -F key=mounts

On a 64 bit system:

Run the following command to verify the rules are contained in a file in the directory: