cis-ubuntu2004-v300-1-7-6

name	cis-ubuntu2004-v300-1-7-6
description	Ensure GDM automatic mounting of removable media is disabled
category	cis-networking
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","gnome","gdm","removable-media","automount"]
cis_id	1.7.6
cis_benchmark	CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

1.7.6 Ensure GDM automatic mounting of removable media is disabled (Automated)

Profile

• Level 1 - Server
• Level 2 - Workstation

Description

By default GNOME automatically mounts removable media when inserted as a convenience to the user.

Rationale

With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in system even if they lacked permissions to mount it themselves.

Impact

The use of portable hard drives is very common for workstation users. If your organization allows the use of portable storage or media on workstations and physical access controls to workstations is considered adequate there is little value add in turning off automounting.

Audit Procedure

Command Line

Run the following command to verify that a user profile exists:

# grep -Psi "user-db|system-db" /etc/dconf/profile/*/*

/etc/dconf/profile/local:user-db:user
/etc/dconf/profile/local:system-db:local

Run the following commands to verify automatic mounting is disabled:

# gsettings get org.gnome.desktop.media-handling automount
false
# gsettings get org.gnome.desktop.media-handling automount-open
false

Expected Result

Both automount and automount-open should be false.

Remediation

Command Line

• IF - A user profile exists run the following commands to ensure automatic mounting is disabled:

# gsettings set org.gnome.desktop.media-handling automount false
# gsettings set org.gnome.desktop.media-handling automount-open false

Note:

• gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned.

• The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess.

• OR/IF - A user profile does not exist:

1. Create a file /etc/dconf/db/local.d/00-media-automount with following content: