The Ubuntu operating system must disable the x86 Ctrl-Alt-Delete key sequence.

A locally logged-on user who presses Ctrl-Alt-Delete, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of a mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot.

Verify the Ubuntu operating system is not configured to reboot the system when Ctrl-Alt-Delete is pressed.

Check that the "ctrl-alt-del.target" (otherwise also known as reboot.target) is not active with the following command:

$ sudo systemctl status ctrl-alt-del.target ctrl-alt-del.target Loaded: masked (Reason: Unit ctrl-alt-del.target is masked.) Active: inactive (dead)

If the "ctrl-alt-del.target" is not masked, this is a finding.

Configure the system to disable the Ctrl-Alt-Delete sequence for the command line with the following commands:

$ sudo systemctl disable ctrl-alt-del.target

$ sudo systemctl mask ctrl-alt-del.target

Reload the daemon to take effect:

$ sudo systemctl daemon-reload