NIST 800-171 3.1.10 (AC.L2-3.1.10): Session Lock

Use session lock with pattern-hiding displays to prevent access and viewing of data after a period of inactivity.

NIST SP 800-171 Rev. 2, requirement 3.1.10

CMMC Level 2 practice AC.L2-3.1.10Published 2026-11-11

What 3.1.10 means in practice

When a user walks away, the screen locks after a set period of inactivity and hides what was on it. Pick the period (15 minutes or less is common), enforce it centrally on every workstation and mobile device, and make sure the lock screen itself shows nothing that reveals CUI.

SPRS points and the CMMC POA&M

CMMC Level 2 practice: AC.L2-3.1.10
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 3.1.10

NIST SP 800-171A gives 3 determination statements for 3.1.10, each found satisfied or other than satisfied. Determine if:

3.1.10[a] the period of inactivity after which the system initiates a session lock is defined.
3.1.10[b] access to the system and viewing of data is prevented by initiating a session lock after the defined period of inactivity.
3.1.10[c] previously visible information is concealed via a pattern-hiding display after the defined period of inactivity.

NIST SP 800-171A (June 2018), assessment objectives for 3.1.10

Evidence that shows 3.1.10 is met

The defined inactivity period before the screen locks.
Group Policy or device management profiles that enforce the screen lock and a password to unlock.
A device compliance report showing the lock setting applied across managed devices.

How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.1.10 from it. Each line says what the product checks.

Microsoft Intune: Compliance policies · Device configurations. Checks that every device Intune manages locks after 15 minutes or less of inactivity and needs a password to unlock.

Related pages

Calculator: SPRS score calculator: mark 3.1.10 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 22 Access Control requirements (3.1).
Previous: 3.1.9: System Use Notices
Next: 3.1.11: Session Termination
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.