NIST SP 800-53 Rev. 5 AC-24 — Access Control Decisions

What this control requires

Establishes procedures or mechanisms to apply organization-defined access control decisions to each access request before enforcement, ensuring authorized access. This control supports the Access Control Module capability within the Access Control family.

In plain English

Establishes procedures or mechanisms to apply organization-defined access control decisions to each access request before enforcement, ensuring authorized access. In practice, this means you can prove you policy procedures-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.

This control is rated high. Auditors expect a named owner, a remediation SLA, and a tooling artefact that evidences continuous operation.

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-24) 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.
• Access Control. Document the trigger, the owner and the cadence.
• Authorized. Document the trigger, the owner and the cadence.
• Mechanisms. Document the trigger, the owner and the cadence.
• Scope: procedures, management, enforcement, access control, organization, decisions, capability, authorized.

Evidence to collect

• Policy Document. A signed and version-controlled policy / standard / procedure document.

Signed policy or standard documents the safeguard. Focus: Access Control Decisions.

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.

• HIPAA (45 CFR Part 164) 164.308(a)(4)(ii)(A) — Information Access Management - Isolating Healthcare Clearinghouse Functions
• NIST SP 800-171 Rev. 3 3.1.5 — Least Privilege

Related controls in NIST SP 800-53 Rev. 5

• Control AC-2(3) — Disable Accounts
• Control AC-4(5) — Embedded Data Types
• Control AC-4(4) — Flow Control Of Encrypted Information
• 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-24

Topics: governance riskpolicy management