Remove the GDM Package Group

Classification:

compliance

Framework:

Control:

Description

By removing the gdm3 package, the system no longer has GNOME installed

installed. If X Windows is not installed then the system cannot boot into graphical user mode. This prevents the system from being accidentally or maliciously booted into a graphical.target mode. To do so, run the following command:

$ sudo apt remove gdm3

Rationale

Unnecessary service packages must not be installed to decrease the attack surface of the system. A graphical environment is unnecessary for certain types of systems including a virtualization hypervisor.

Remediation

Shell script

The following script can be run on the host to remediate the issue.

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'gdm3' 2>/dev/null | grep -q installed; then

# CAUTION: This remediation script will remove gdm3
# from the system, and may remove any packages
# that depend on gdm3. Execute this
# remediation AFTER testing on a non-production
# system!

DEBIAN\_FRONTEND=noninteractive apt-get remove -y "gdm3"

else
 >&2 echo 'Remediation is not applicable, nothing was done'
fi

Ansible playbook

The following playbook can be run with Ansible to remediate the issue.

- name: Gather the package facts
 package\_facts:
 manager: auto
 tags:
 - NIST-800-53-CM-6(a)
 - NIST-800-53-CM-7(a)
 - NIST-800-53-CM-7(b)
 - disable\_strategy
 - low\_complexity
 - low\_disruption
 - medium\_severity
 - no\_reboot\_needed
 - package\_gdm\_removed

- name: Ensure gdm3 is removed
 package:
 name: gdm3
 state: absent
 when: '"gdm3" in ansible\_facts.packages'
 tags:
 - NIST-800-53-CM-6(a)
 - NIST-800-53-CM-7(a)
 - NIST-800-53-CM-7(b)
 - disable\_strategy
 - low\_complexity
 - low\_disruption
 - medium\_severity
 - no\_reboot\_needed
 - package\_gdm\_removed