cis-ubuntu2004-v300-1-7-9

DevOps & Security

Ensure GDM autorun-never is not overridden

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1.7.9 Ensure GDM autorun-never is not overridden (Automated)

Profile

Level 1 - Server
Level 1 - Workstation

Description

The autorun-never setting allows the GNOME Desktop Display Manager to disable autorun through GDM.

By using the lockdown mode in dconf, you can prevent users from changing specific settings.

To lock down a dconf key or subpath, create a locks subdirectory in the keyfile directory. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory.

Rationale

Malware on removable media may taking advantage of Autorun features when the media is inserted into a system and execute.

Audit Procedure

Command Line

Run the following command to verify that autorun-never=true cannot be overridden:

# grep -Psi "autorun-never" /etc/dconf/db/*/locks/*

/etc/dconf/db/local.d/locks/00-media-autorun:autorun-never=true

Expected Result

Lock entry for autorun-never should be present.

Remediation

Command Line

To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/00-media-autorun with the following content:

[org/gnome/desktop/media-handling]
autorun-never=true

Update the systems databases:

# dconf update

Note:

A user profile must exist in order to apply locks. If a user profile does not exist review the remediation steps in the previous recommendation.
Users must log out and back in again before the system-wide settings take effect.

References

NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	10.3 Disable Autorun and Autoplay for Removable Media	*	*	*
v7	8.5 Configure Devices Not To Auto-run Content	*	*	*

MITRE ATT&CK Mappings: T1091, T1091.000 | TA0001, TA0008 | M1028