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The Ubuntu Operating system must disable the x86 Ctrl-Alt-Delete key sequence if a graphical user interface is installed.


Finding ID Version Rule ID IA Controls Severity
V-219211 UBTU-18-010150 SV-219211r610963_rule High
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. In the graphical environment, risk of unintentional reboot from the Ctrl-Alt-Delete sequence is reduced because the user will be prompted before any action is taken.
Canonical Ubuntu 18.04 LTS Security Technical Implementation Guide 2022-12-06


Check Text ( C-20936r304961_chk )
Verify the Ubuntu operating system is not configured to reboot the system when Ctrl-Alt-Delete is pressed when using a graphical user interface.

Check that the "logout" target is not bound to an action with the following command:

# grep logout /etc/dconf/db/local.d/*


If the "logout" key is bound to an action, is commented out, or is missing, this is a finding.
Fix Text (F-20935r304962_fix)
Configure the system to disable the Ctrl-Alt-Delete sequence when using a graphical user interface by creating or editing the /etc/dconf/db/local.d/00-disable-CAD file.

Add the setting to disable the Ctrl-Alt-Delete sequence for the graphical user interface:


Then update the dconf settings:

# dconf update