4.16. Thumbnail Protection

The thumbnail icons can potentially allow an attacker to break into a locked machine using removable media, such as USB devices or CDs. When the system detects a removable media, the Nautilus file manager executes the thumbnail driver code to display thumbnail icons in an appropriate file browser even if the machine is locked. This behavior is unsafe because if the thumbnail executables were vulnerable, the attacker could use the thumbnail driver code to bypass the lock screen without entering the password.

Therefore, a new SELinux policy is used to prevent such attacks. This policy ensures that all thumbnail drivers are locked when the screen is locked. The thumbnail protection is enabled for both confined users and unconfined users. This policy affects the following applications: