NIST 800-171 3.13.16 (SC.L2-3.13.16): CUI at Rest

Protect the confidentiality of CUI at rest.

NIST SP 800-171 Rev. 2, requirement 3.13.16

CMMC Level 2 practice SC.L2-3.13.16Published 2026-11-11

What 3.13.16 means in practice

CUI stored on servers, laptops, databases, cloud storage and backups is protected, usually by encryption at rest, so a stolen disk or an exposed storage account does not expose it. Where encryption cannot give adequate protection, NIST's discussion names other means, such as keeping the data in secure offline storage.

SPRS points and the CMMC POA&M

CMMC Level 2 practice: SC.L2-3.13.16
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 3.13.16

NIST SP 800-171A gives one determination statement for 3.13.16.

Determine if the confidentiality of CUI at rest is protected.

NIST SP 800-171A (June 2018), assessment objectives for 3.13.16

Evidence that shows 3.13.16 is met

Disk and storage encryption settings for servers, endpoints and cloud storage.
Database encryption settings.
The list of places where CUI is stored and how each is protected.

How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.13.16 from it. Each line says what the product checks.

Azure Storage: Storage accounts; Azure: Virtual machines and disks. Checks that every Azure Storage account and managed disk is encrypted at rest.
AWS: S3 buckets · EC2 and VPC networking · Data stores · CloudTrail and CloudWatch · Load balancers, API Gateway, CloudFront and Lambda. Checks encryption at rest across AWS: S3 default encryption, EBS volumes, RDS, EFS, DynamoDB, Redshift, ElastiCache, SNS topics, CloudWatch log groups and API Gateway caches.

Related pages

Calculator: SPRS score calculator: mark 3.13.16 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 16 System and Communications Protection requirements (3.13).
Previous: 3.13.15: Session Authenticity
Next: 3.14.1: Flaw Remediation
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.