cis-ubuntu1204-v110-2-23

name	cis-ubuntu1204-v110-2-23
description	Disable Mounting of squashfs Filesystems
category	cis-os-hardening
version	1.1.0
author	cyberstrike-official
tags	["cis","ubuntu",12.04,"linux","filesystem","squashfs","kernel-module","attack-surface"]
cis_id	2.23
cis_benchmark	CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

2.23 Disable Mounting of squashfs Filesystems (Not Scored)

Profile Applicability

• Level 2

Description

The squashfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems (similar to cramfs). A squashfs image can be used without having to first decompress the image.

Rationale

Removing support for unneeded filesystem types reduces the local attack surface of the server. If this filesystem type is not needed, disable it.

Audit Procedure

Using Command Line

/sbin/modprobe -n -v squashfs
/sbin/lsmod | grep squashfs

Expected Result

The first command should output install /bin/true. The second command should produce no output (module not loaded).

Remediation

Using Command Line

Edit or create the file /etc/modprobe.d/CIS.conf and add the following line:

install squashfs /bin/true

Default Value

By default, the squashfs module is available for loading.

References

• CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0

Profile

Level 2 - Not Scored