NIST SP 800-53 Rev. 5 AC-2(5) — Inactivity Logout

What this control requires

Require users to log out after an organization-defined time period of expected inactivity or based on a specific description of when to log out. This control supports the Governance capability within the Access Control family.

In plain English

Require users to log out after an organization-defined time period of expected inactivity or based on a specific description of when to log out. 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-2(5)) and look for objective evidence on the latest two assessment cycles.

How to implement

Logging Monitoring

AWS. Org-trail CloudTrail to a central log archive account, GuardDuty in every region, and Security Hub for cross-source correlation.

Azure. Pipe every diagnostic setting into a central Log Analytics workspace; onboard Microsoft Sentinel for SIEM/SOAR.

GCP. Aggregate audit logs in a dedicated logging project with sink to BigQuery; enable Security Command Center Premium and route findings to Chronicle SIEM.

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.
• Inactivity. 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.
• Time. Document the trigger, the owner and the cadence.
• Scope: management, logout, access control, organization, time, time period, capability, policy.

Evidence to collect

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

Signed policy or standard documents the safeguard. Focus: Inactivity Logout.

Common pitfalls

• Per-account logging that nobody stitches together at the org level — incidents that cross accounts go undetected for days.
• 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 3.1.5 — Least Privilege
• HIPAA (45 CFR Part 164) 164.310(a)(2)(iii) — Facility Access Controls - Access Control and Validation Procedures
• ISO/IEC 27001:2022 A.8.15 — Logging
• BSI C5:2020 SP-01 — Documentation, communication and provision of policies and instructions

Related controls in NIST SP 800-53 Rev. 5

• Control AC-2(3) — Disable Accounts
• Control AC-2(2) — Automated Temporary And Emergency Account Management
• Control AC-12(3) — Timeout Warning Message
• Control AC-20(5) — Portable Storage Devices -- Prohibited Use
• Control AC-24 — Access Control Decisions
• Control AC-4(26) — Audit Filtering Actions

References

• NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5
• Catalogue identifier: Control AC-2(5)

Topics: governance risklogging monitoringpolicy management