AC.L2-3.1.21 — Limit portable storage on external systems
Limit use of portable storage devices on external systems.
Verbatim NIST SP 800-171 Rev 2 requirement text (3.1.21).
How it's scored
1 point deducted from your SPRS score if unmet.
An open gap here may sit on a POA&M at conditional Level 2 certification (32 CFR 170.21), provided your total score is at least 88 of 110 — and it must close within 180 days of the conditional status date.
What an assessor checks: the 3 assessment objectives
NIST SP 800-171A determination statements, verbatim. A CMMC Level 2 assessor marks AC.L2-3.1.21 MET only when every applicable objective is satisfied — and examines evidence, not assertions.
| Objective | Determination statement |
|---|---|
| 3.1.21[a] | use of organizational portable storage devices containing CUI on external systems is identified and documented. |
| 3.1.21[b] | limits on the use of organizational portable storage devices containing CUI on external systems are defined. |
| 3.1.21[c] | use of organizational portable storage devices containing CUI on external systems is limited as defined. |
Where do you stand on AC.L2-3.1.21?
The free Muster Score walks all 110 requirements — including every objective above — and computes your exact SPRS score in your browser. No signup, no upload, and your answers never leave your device.
Get your free Muster Score →Requirement and objective text: NIST SP 800-171 Rev 2 / SP 800-171A (verbatim). Scoring: DoD Assessment Methodology v1.2.1; POA&M eligibility: 32 CFR 170.21. Muster is independent and not affiliated with the U.S. Department of Defense or the Cyber AB; this page is compliance information, not legal advice or a certification.