# Cis Ubuntu1804 V220 1 8 9 > Ensure GDM autorun-never is not overridden - Skill: `cyberstrikeus/cis-ubuntu1804-v220-1-8-9` (Agent Skill) - Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1804-v220-1-8-9` - Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1804-v220-1-8-9/raw - Safety review: PASS (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/cyberstrikeus/cis-ubuntu1804-v220-1-8-9 --- # 1.8.9 Ensure GDM autorun-never is not overridden (Automated) ## Profile Applicability - 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. Example Lock File: ``` # Lock desktop media-handling settings /org/gnome/desktop/media-handling/autorun-never ``` ## 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 script to verify that `autorun-never=true` cannot be overridden: ```bash #!/usr/bin/env bash { # Check if GNOME Desktop Manager is installed. If package isn't installed, recommendation is Not Applicable\n # determine system's package manager l_pkgoutput="" if command -v dpkg-query > /dev/null 2>&1; then l_pq="dpkg-query -s" elif command -v rpm > /dev/null 2>&1; then l_pq="rpm -q" fi # Check if GDM is installed l_pcl="gdm gdm3" # Space separated list of packages to check for l_pn in $l_pcl; do $l_pq "$l_pn" > /dev/null 2>&1 && l_pkgoutput="$l_pkgoutput\n - Package: \"$l_pn\" exists on the system\n - checking configuration" done # Check configuration (If applicable) if [ -n "$l_pkgoutput" ]; then l_output="" l_output2="" # Look for idle-delay to determine profile in use, needed for remaining tests l_kfd="/etc/dconf/db/$(grep -Psril '^\h*autorun-never\b' /etc/dconf/db/*/ | awk -F'/' '{split($(NF-1),a,".");print a[1]}').d" #set directory of key file to be locked if [ -d "$l_kfd" ]; then # If key file directory doesn't exist, options can't be locked if grep -Prisq '^\h*\/org\/gnome\/desktop\/media-handling\/autorun-never\b' "$l_kfd"; then l_output="$l_output\n - \"autorun-never\" is locked in \"$(grep -Pril '^\h*\/org\/gnome\/desktop\/media-handling\/autorun-never\b' "$l_kfd")\"" else l_output2="$l_output2\n - \"autorun-never\" is not locked" fi else l_output2="$l_output2\n - \"autorun-never\" is not set so it can not be locked" fi else l_output="$l_output\n - GNOME Desktop Manager package is not installed on the system\n - Recommendation is not applicable" fi # Report results. If no failures output in l_output2, we pass [ -n "$l_pkgoutput" ] && echo -e "\n$l_pkgoutput" if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **\n$l_output\n" else echo -e "\n- Audit Result:\n ** FAIL **\n - Reason(s) for audit failure:\n$l_output2\n" [ -n "$l_output" ] && echo -e "\n- Correctly set:\n$l_output\n" fi } ``` ## Remediation ### Command Line Run the following script to ensure that `autorun-never=true` cannot be overridden: ```bash #!/usr/bin/env bash { # Check if GNOME Desktop Manager is installed. If package isn't installed, recommendation is Not Applicable\n # determine system's package manager l_pkgoutput="" if command -v dpkg-query > /dev/null 2>&1; then l_pq="dpkg-query -s" elif command -v rpm > /dev/null 2>&1; then l_pq="rpm -q" fi # Check if GDM is installed l_pcl="gdm gdm3" # Space separated list of packages to check for l_pn in $l_pcl; do $l_pq "$l_pn" > /dev/null 2>&1 && l_pkgoutput="$l_pkgoutput\n - Package: \"$l_pn\" exists on the system\n - remediating configuration if needed" done # Check configuration (If applicable) if [ -n "$l_pkgoutput" ]; then # Look for autorun to determine profile in use, needed for remaining tests l_kfd="/etc/dconf/db/$(grep -Psril '^\h*autorun-never\b' /etc/dconf/db/*/ | awk -F'/' '{split($(NF-1),a,".");print a[1]}').d" #set directory of key file to be locked if [ -d "$l_kfd" ]; then # If key file directory doesn't exist, options can't be locked if grep -Priq '^\h*\/org\/gnome\/desktop\/media-handling\/autorun-never\b' "$l_kfd"; then echo " - \"autorun-never\" is locked in \"$(grep -Pril '^\h*\/org\/gnome\/desktop\/media-handling\/autorun-never\b' "$l_kfd")\"" else echo " - creating entry to lock \"autorun-never\"" { ! -d "$l_kfd"/locks } && echo "creating directory $l_kfd/locks" && mkdir "$l_kfd"/locks { echo -e '\n# Lock desktop media-handling autorun-never setting' echo '/org/gnome/desktop/media-handling/autorun-never' } >> "$l_kfd"/locks/00-media-autorun fi else echo -e " - \"autorun-never\" is not set so it can not be locked\n - Please follow Recommendation \"Ensure GDM autorun-never is enabled\" and follow this Recommendation again" fi # update dconf database dconf update else echo -e " - GNOME Desktop Manager package is not installed on the system\n - Recommendation is not applicable" fi } ``` ## References 1. 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 | X | X | X | | v7 | 8.5 Configure Devices Not To Auto-run Content | X | X | X | ## MITRE ATT&CK Mappings | Techniques / Sub-techniques | Tactics | Mitigations | | --------------------------- | -------------- | ----------- | | T1091, T1091.000 | TA0001, TA0008 | M1028 |