NIST 800-171 3.4.9 (CM.L2-3.4.9): User-Installed Software

Control and monitor user-installed software.

NIST SP 800-171 Rev. 2, requirement 3.4.9

CMMC Level 2 practice CM.L2-3.4.9Published 2026-11-11

What 3.4.9 means in practice

Decide whether users may install software and under what rules, enforce the decision (for example by removing local administrator rights or offering an approved software catalog), and watch for installations that break the rules. Updates and security patches from an approved catalog are the typical permitted installations; software of unknown or suspect origin is the typical prohibited one.

SPRS points and the CMMC POA&M

CMMC Level 2 practice: CM.L2-3.4.9
SPRS points: 1 point. When it is not met, the DoD Assessment Methodology subtracts 1 from the score of 110.
CMMC POA&M: Allowed. It is worth 1 point, and 32 CFR 170.21(a)(2)(ii) admits requirements worth 1 point. Conditional status also needs a score of at least 88, and the item must be closed within 180 days.

Sources: NIST SP 800-171 DoD Assessment Methodology, version 1.2.1 (June 24, 2020), Annex A; 32 CFR 170.21, Plan of Action and Milestones requirements.

What an assessor checks for 3.4.9

NIST SP 800-171A gives 3 determination statements for 3.4.9, each found satisfied or other than satisfied. Determine if:

3.4.9[a] a policy for controlling the installation of software by users is established.
3.4.9[b] installation of software by users is controlled based on the established policy.
3.4.9[c] installation of software by users is monitored.

NIST SP 800-171A (June 2018), assessment objectives for 3.4.9

Evidence that shows 3.4.9 is met

The policy on software installation by users.
Configuration that prevents unapproved installations, such as the absence of local administrator rights.
Software inventory reports or alerts that reveal software users installed.

How PolicyCortex gathers the evidence

No PolicyCortex collector reads the evidence for 3.4.9. Your team provides the evidence listed above.

Related pages

Calculator: SPRS score calculator: mark 3.4.9 and the other 109 requirements and see the score.
Sample package: Sample package: an SSP, a POA&M and an evidence chain the product generated from demonstration data.
Family: All 9 Configuration Management requirements (3.4).
Previous: 3.4.8: Application Execution
Next: 3.5.1: Identification
All requirements: All 110 NIST SP 800-171 requirements, by family.

Related records

Guides and articles describe the work. The evidence that work produces is described in three proof pages, the architecture page, and the two pages on authorization.

proof.state: Proof of State. What the environment was, as of a date someone else picks: point-in-time records, content hashed and chained.
proof.change: Proof of Change. Who or what altered the environment, under what authority, with before and after state hashes.
proof.agency: Proof of Agency. What a machine was permitted to do before it acted, what it did, and what would have stopped it.
architecture: Architecture. How the chain is built and where the evidence is stored in each delivery mode.
authorization: Continuous ATO. How an authorizing official's decision is recorded with its package, and how the authorized system is checked against it every hour.
baseline: NIST SP 800-53. The Low, Moderate and High baselines as evidence, with the SSP, SAR and POA&M generated from one record.