Cloud Linux AlmaLinux OS 9 Security Technical Implementation Guide

The Cloud Linux AlmaLinux OS 9 Security Technical Implementation Guide (V1 R8) has 439 STIG checks. New to STIG checklists? Read What is a STIG checklist?, CKL vs CKLB, and STIG vs SCAP benchmark.

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Severity

Version

V1 · R8

CurrentPublished Wed Sep 30 2026

AlmaLinux OS 9 must disable mounting of udf.

Cloud Linux AlmaLinux OS 9 Security Technical Implementation Guide

Assessment Title

Rule Text

AlmaLinux OS 9 must disable mounting of udf.

Description

Discussion Text

Removing support for unneeded filesystem types reduces the local attack surface of the server.

The UDF filesystem is used to write DVDs and so could assist in data exfiltration, the so-called "sneakernet".

Note that Microsoft Azure uses UDF.

New to STIG checklists? Read What is a STIG checklist? and CKL vs CKLB.

Objective

V-269348

Rule

SV-269348r1050230_rule

Severity

medium

Rule Version

ALMA-09-030380

Documentable

false

IA Controls

NIST SP 800-53

Rev 5

Assessment Procedure

Check Text

Verify that AlmaLinux OS 9 disables the ability to load the udf kernel module with the following command:

$ grep udf /etc/modprobe.conf /etc/modprobe.d/* 

blacklist udf

If the command does not return any output, or the line is commented out, and use of UDF is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding.

Implementation Procedure

Fix Text

To configure the system to prevent the udf kernel module from being loaded, create a *.conf file in /etc/modprobe.d/ with the following content:

install udf /bin/false
blacklist udf

STIG check 238 of 439 in the Cloud Linux AlmaLinux OS 9 STIG checklist

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