Linux - System Preferences - Ensure Mounting of Udf Filesystems is Disabled

What the udf filesystem disabler does

This Automox Worklet™ disables mounting of udf (Universal Disk Format) filesystems on Linux endpoints. The Worklet first checks whether the udf module is currently loaded on the system, then prevents future mounting by creating a kernel module configuration file.

The Worklet modifies `/etc/modprobe.d/udf.conf` to blacklist the udf module, preventing the kernel from loading it during boot or during runtime module loading operations. This approach maintains the filesystem remains disabled across system reboots.

Why disable udf filesystem support

Legacy filesystem support expands your attack surface by introducing older, less-maintained kernel code paths. The udf filesystem is rarely used in modern Linux deployments, making it an unnecessary vector for potential exploits.

Disabling udf aligns with the CIS Distribution Independent Linux Benchmarks, which recommend removing support for unused filesystems. This hardening step reduces kernel complexity and closes potential privilege escalation paths that could be exposed through kernel vulnerabilities.

Organizations subject to compliance frameworks such as NIST, SOC 2, or PCI-DSS benefit from reducing the kernel attack surface. Disabling unused filesystem support is a foundational security control that complements other endpoint hardening measures.

How udf filesystem disabling works

1. Evaluation phase: Checks if the udf module configuration exists using modprobe and verifies whether the module is currently loaded by examining the output of lsmod. The Worklet exits with no changes if udf is not present or not loaded.

2. Remediation phase: Creates `/etc/modprobe.d/udf.conf` with the entry "install udf /bin/true", which redirects module installation to a null operation. Unloads the currently running module using rmmod. Verifies that the module is no longer loaded.

udf filesystem disabling requirements

• Linux-based endpoints (workstations or servers)

• Root or sudo privileges to modify kernel module configuration

• Automox Agent version 1.42.22 or later

• udf module must be installed for the Worklet to execute (no action if not present)

• RunNow capability enabled for immediate execution

Expected udf module state after remediation

After the Worklet executes successfully, the udf module will be unloaded from kernel memory and prevented from loading in future boot cycles. The configuration file `/etc/modprobe.d/udf.conf` will remain in place to enforce the policy across system reboots and kernel updates.

Verify the remediation by running the command "lsmod | grep udf" on the endpoint. The output should be empty, confirming that the module is not loaded. As this is a kernel-level change, some systems may require a reboot for full compliance if the module was loaded before remediation.

How to validate verify mounting of udf filesystems is disabled changes

1. Run this Worklet on a pilot Linux endpoint and review evaluation output for verify mounting of udf filesystems is disabled.

2. Confirm Automox activity logs show successful completion and exit code 0.

3. Verify endpoint state using checks aligned to evaluation script logic, such as else, exit.

4. Validate remediation effects from script operations such as function, touch, rmmod, then rerun evaluation for compliance.

For technical validation, compare endpoint state to the Worklet evaluation logic and remediation flow for verify mounting of udf filesystems is disabled. This supports repeatable system preferences workflows, faster change control review, and auditable compliance evidence.

Useful script references for this Worklet include evaluation operations such as else, exit and remediation operations such as function, touch, rmmod. Use these indicators to verify that endpoint changes match intended policy outcomes.