Vulnerability Discussion
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.
Check
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.
Fix
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