A session time-out lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not log out because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, operating systems need to be able to identify when a user's session has idled and take action to initiate the session lock.
The session lock is implemented at the point where session activity can be determined and/or controlled.
Check
Verify TOSS initiates a session lock after at most a 15-minute period of inactivity for graphical user interfaces with the following commands:
Note: This requirement assumes the use of the TOSS default graphical user interface, Gnome Shell. If the system does not have any graphical user interface installed, this requirement is Not Applicable.
$ sudo gsettings get org.gnome.desktop.session idle-delay uint32 900
If "idle-delay" is set to "0" or a value greater than "900", this is a finding.
Fix
Configure the operating system to initiate a screensaver after a 15-minute period of inactivity for graphical user interfaces.
Create a database to contain the system-wide screensaver settings (if it does not already exist) with the following command:
$ sudo touch /etc/dconf/db/local.d/00-screensaver
Edit /etc/dconf/db/local.d/00-screensaver and add or update the following lines:
[org/gnome/desktop/session] # Set the lock time out to 900 seconds before the session is considered idle idle-delay=uint32 900