cis-ubuntu1604-v200-1-8-3

name	cis-ubuntu1604-v200-1-8-3
description	Ensure disable-user-list is enabled
category	cis-iam
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","gdm","gnome","user-list","login","display-manager"]
cis_id	1.8.3
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 - 1.8.3

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

GDM is the GNOME Display Manager which handles graphical login for GNOME based systems.

The disable-user-list option controls is a list of users is displayed on the login screen.

Rationale

Displaying the user list eliminates half of the Userid/Password equation that an unauthorized person would need to log on.

Audit Procedure

Command Line

Run the following command to verify that disable-user-list is enabled:

grep -E '^\s*disable-user-list\s*=\s*true\b' /etc/gdm3/greeter.dconf-defaults

Expected output: disable-user-list=true

Expected Result

The disable-user-list option should be set to true in the GDM configuration.

Remediation

Command Line

Edit or create the file /etc/gdm3/greeter.dconf-defaults and edit or add the following:

[org/gnome/login-screen]
banner-message-enable=true
banner-message-text='<banner message>'
disable-user-list=true

Run the following command to re-load GDM on the next login or reboot:

dpkg-reconfigure gdm3

Additional Information

If a different GUI login service is in use and required on the system, consult your documentation to disable displaying the user list.

Default Value

false

References

None.

CIS Controls

Controls Version	Control
v7	5.1 Establish Secure Configurations

Assessment Status

Automated