Internet services that are not required for system or application processes must not be active to decrease the attack surface of the system. Graphical display managers have a long history of security vulnerabilities and must not be used, unless approved and documented.
Check
Verify that the system is configured to boot to the command line:
$ systemctl get-default multi-user.target
If the system default target is not set to "multi-user.target" and the Information System Security Officer (ISSO) lacks a documented requirement for a graphical user interface, this is a finding.
Fix
Document the requirement for a graphical user interface with the ISSO or reinstall the operating system without the graphical user interface. If reinstallation is not feasible, then continue with the following procedure:
Open an SSH session and enter the following commands:
$ sudo systemctl set-default multi-user.target
A reboot is required for the changes to take effect.