NIST SP 800-53 Rev. 5 AC-20(5) — Portable Storage Devices -- Prohibited Use

What this control requires

Prohibits use of organization-controlled portable storage devices on external systems, enforced via technical or process-based methods to prevent data compromise. This control supports the Device Management Policy capability within the Access Control family.

In plain English

Prohibits use of organization-controlled portable storage devices on external systems, enforced via technical or process-based methods to prevent data compromise. In practice, this means you can prove you policy management-level controls on a defined cadence.

Why it matters

SP 800-53 is the catalogue every U.S. federal authorisation (FedRAMP, FISMA, CMMC) and most regulated industries point at. A missing control surfaces as a Plan of Action & Milestones (POA&M) item that an Authorizing Official must approve before the Authority To Operate is granted or renewed.

What an auditor looks for

A 3PAO (FedRAMP) or Independent Assessor (NIST RMF) tests against NIST SP 800-53A assessment procedures. For each control they expect a documented implementation that addresses every assessment objective (Examine, Interview, Test) and an implementation summary in the System Security Plan.

Within Access Control, the assessor will trace your implementation back to the catalogue reference (Control AC-20(5)) and look for objective evidence on the latest two assessment cycles.

How to implement

Policy Management

Docs. Keep each policy in version-controlled Markdown alongside the code that implements it; ship a signed PDF snapshot at each annual review and link the SHA into the SoA.

Operational checklist

• Policy. Document the trigger, the owner and the cadence.
• Access. Document the trigger, the owner and the cadence.
• Process. Document the trigger, the owner and the cadence.
• Data. Document the trigger, the owner and the cadence.
• Device. Document the trigger, the owner and the cadence.
• Scope: management, access control, organization, external systems, capability, storage, policy, devices.

Evidence to collect

• Policy Document. A signed and version-controlled policy / standard / procedure document.
• Infra Scan. Continuous infrastructure-posture telemetry — AWS Config, Azure Policy compliance, GCP Organisation Policy, Wiz / Prisma findings.

Signed policy or standard documents the safeguard. Focus: Portable Storage Devices -- Prohibited Use.

Common pitfalls

• Policies that no engineer has read; the version in Confluence drifts from the version that's actually being enforced.

How it maps to other frameworks

Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit.

• NIST SP 800-171 Rev. 3 3.1.20 — Use of External Systems
• HIPAA (45 CFR Part 164) 164.310(a)(2)(iii) — Facility Access Controls - Access Control and Validation Procedures

Related controls in NIST SP 800-53 Rev. 5

• Control AC-20(2) — Portable Storage Devices -- Restricted Use
• Control AC-2(3) — Disable Accounts
• Control AC-20 — Use Of External Systems
• Control AC-2(2) — Automated Temporary And Emergency Account Management
• Control AC-2(5) — Inactivity Logout
• Control AC-4 — Information Flow Enforcement

References

• NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5
• Catalogue identifier: Control AC-20(5)

Topics: governance riskpolicy management