The Ubuntu operating system must be configured so that Advance Package Tool (APT) removes all software components after updated versions have been installed.

Previous versions of software components that are not removed from the information system after updates have been installed may be exploited by adversaries. Some information technology products may remove older versions of software automatically from the information system.

Verify is configured to remove all software components after updated versions have been installed with the following command:

$ grep -i remove-unused /etc/apt/apt.conf.d/50unattended-upgrades Unattended-Upgrade::Remove-Unused-Dependencies "true"; Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";

If the "::Remove-Unused-Dependencies" and "::Remove-Unused-Kernel-Packages" parameters are not set to "true" or are missing or commented out, this is a finding.

Configure APT to remove all software components after updated versions have been installed.

Add or updated the following options to the "/etc/apt/apt.conf.d/50unattended-upgrades" file:

Unattended-Upgrade::Remove-Unused-Dependencies "true"; Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";