Session Lock
Use session lock with pattern- hiding displays to prevent access and viewing of data after a period of inactivity.
What an assessor scores, the objectives
AC.L2-3.1.10 is met only when every one of these 3 objectives, from NIST SP 800-171A, is satisfied. A single missed objective makes the whole requirement not met.
- a.the period of inactivity after which the system initiates a session lock is defined
- b.access to the system and viewing of data is prevented by initiating a session lock after the defined period of inactivity
- c.previously visible information is concealed via a pattern-hiding display after the defined period of inactivity
How a C3PAO checks it
NIST SP 800-171A defines three assessment methods. For AC.L2-3.1.10, an assessor uses these:
Access control policy; procedures addressing session lock; procedures addressing identification and authentication; system design documentation; system configuration settings and associated documentation; system security plan; other relevant documents or records
System or network administrators; personnel with information security responsibilities; system developers
Mechanisms implementing access control policy for session lock
What it means, in context
Session locks are temporary actions taken when users stop work and move away from the immediate vicinity of the system but do not want to log out because of the temporary nature of their absences. Session locks are implemented where session activities can be determined, typically at the operating system level (but can also be at the application level). Session locks are not an acceptable substitute for logging out of the system, for example, if organizations require users to log out at the end of the workday. Pattern-hiding displays can include static or dynamic images, for example, patterns used with screen savers, photographic images, solid colors, clock, battery life indicator, or a blank screen, with the additional caveat that none of the images convey controlled unclassified information.
Session locks can be initiated by the user or, more fundamentally, enabled automatically when the system has been idle for a period of time, for example, five minutes. Session locks are a quick way to prevent unauthorized use of the systems without having a user log off. Minimum configuration requirements are left up to the organization to define. A locked session shows pattern- hiding information on the screen to mask the data on the display. Example You manage systems for an organization that stores, processes, and transmits CUI . You notice that employees leave their offices without locking their computers. Sometimes their screens display sensitive company information. You configure all machines to lock after five minutes of inactivity [a,b]. You also remind your coworkers to lock their systems when they walk away [a]. Potential Assessment Considerations • Does the session lock hide previously visible information (e.g., replacing what was visible with a lock screen or screensaver that does not include sensitive information) [c]? • If session locks are not managed centrally, how are all computer users made aware of the requirements and how to configure them [a,b,c]?
What passing evidence looks like
The screen lock timeout setting from the tool that enforces it, plus your defined inactivity period written in policy. The lock screen must hide what was on screen.
Common ways contractors fail AC.L2-3.1.10
- !The period must be DEFINED first, objective [a]. Pick a number (15 minutes is common), write it down, then show the enforcement matches it.
The step by step walkthrough for Microsoft 365 GCC High, Google Workspace, and on premises setups, plus the exact evidence to capture, lives inside the Level 2 Accelerator.
Prove AC.L2-3.1.10, and the other 109
The Level 2 Accelerator walks all 110 requirements with you, generates your SSP, POA&M, and Audit Room from real evidence, includes the full Level 1 platform, and puts a credentialed officer alongside you for 180 days. Filed in 180 days, or we work free until you are.
No credit card. Phase 2 begins Nov 10, 2026, when applicable DoD solicitations start requiring a current Level 2 status to win the award.
AC.L2-3.1.10 questions, answered
How many points is CMMC requirement AC.L2-3.1.10 worth?+
AC.L2-3.1.10 is worth 1 point in the CMMC Level 2 score under 32 CFR 170.24. If it is not met, you lose 1 from your total of 110.
Can AC.L2-3.1.10 be placed on a POA&M?+
Yes. A gap on AC.L2-3.1.10 can be deferred to a Plan of Action and Milestones, provided your overall score is 88 or better and the item closes within 180 days.
What family does AC.L2-3.1.10 belong to?+
AC.L2-3.1.10 is in the Access Control (AC) family, one of the 14 families of NIST SP 800-171 that make up CMMC Level 2.
- NIST SP 800-171 Rev. 2 3.1.10