Vulnerability Discussion

Setting the screensaver mode to blank-only conceals the contents of the display from passersby.

Check

Note: This requirement assumes the use of the Ubuntu 24.04 LTS default graphical user interface, the GNOME desktop environment. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

To verify the screensaver is configured to be blank, run the following command:

$ gsettings writable org.gnome.desktop.screensaver picture-uri

false

If "picture-uri" is writable and the result is "true", this is a finding.

Fix

Configure Ubuntu 24.04 LTS to prevent a user from overriding the picture-uri setting for graphical user interfaces.

In the file "/etc/dconf/db/local.d/00-security-settings", add or update the following lines:

[org/gnome/desktop/screensaver]
picture-uri=''

Prevent user modification by adding the following line to "/etc/dconf/db/local.d/locks/00-security-settings-lock":

/org/gnome/desktop/screensaver/picture-uri

Update the dconf system databases:

$ sudo dconf update