CUI sitting on disks, laptops, and drives should be encrypted.
What it actually means
Protect the confidentiality of CUI at rest — stored on servers, workstations, laptops, and removable media. Full-disk encryption (BitLocker, FileVault) on every device that holds CUI is the standard approach, plus encryption for backups and removable media. Pair it with FIPS-validated cryptography (3.13.11).
Pass or fail — an assessor needs a "yes" to each
- Is full-disk encryption enabled on all devices that store CUI, including laptops?
- Are backups and removable media holding CUI encrypted?
What to have ready
- Encryption status report (BitLocker / FileVault) across devices
- Backup and removable-media encryption configuration
Where teams trip up
- Desktops and servers left unencrypted because 'they don't leave the building'
- Encrypted laptops but plaintext backups
To fully satisfy this alongside 3.13.11, the at-rest encryption must be FIPS-validated. Most BitLocker / FileVault deployments can run in a FIPS-validated mode.
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More in System & Communications Protection (3.13)
3.13.1 — Protect your boundaries3.13.2 — Build security in by design3.13.3 — Separate user and admin functions3.13.4 — Stop data leaking through shared resources3.13.5 — Wall off your public-facing systems3.13.6 — Deny all, permit by exception3.13.7 — Block split tunneling on VPNs3.13.8 — Encrypt CUI in transit3.13.9 — Drop idle network sessions3.13.10 — Manage your encryption keys3.13.11 — FIPS-validated cryptography3.13.12 — Control cameras and microphones3.13.13 — Control mobile code3.13.14 — Control and monitor VoIP3.13.15 — Protect session authenticity