NIST SP 800-53 Rev. 5 SC-23(3) — Unique System-Generated Session Identifiers

What this control requires

Generate a unique session identifier for each session with organization-defined randomness requirements and recognize only system-generated session identifiers. This approach prevents adversaries from reusing valid session IDs and protects against brute-force attacks aimed at predicting future session identifiers. This control supports the Session Identifier Generation System capability within the System and Communications Protection family.

In plain English

Generate a unique session identifier for each session with organization-defined randomness requirements and recognize only system-generated session identifiers. 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.

This control is rated critical in the source catalogue. Treat gaps here as production incidents in the risk register, not housekeeping.

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 System and Communications Protection, the assessor will trace your implementation back to the catalogue reference (Control SC-23(3)) 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.
• Session. Document the trigger, the owner and the cadence.
• Protection. Document the trigger, the owner and the cadence.
• System. Document the trigger, the owner and the cadence.
• Control. Document the trigger, the owner and the cadence.
• Scope: management, organization, system, only, protection, generation, capability, policy.

Evidence to collect

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

Signed policy or standard documents the safeguard. Focus: Unique System-Generated Session Identifiers.

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) 164.502(j)(2) — Disclosures by workforce members who are victims of a crime
• NIST SP 800-171 Rev. 3 3.14.3 — Security Alerts, Advisories, and Directives
• ISO/IEC 27001:2022 A.8.26 — Application security requirements
• BSI C5:2020 SP-01 — Documentation, communication and provision of policies and instructions

Related controls in NIST SP 800-53 Rev. 5

• Control SC-15(4) — Explicitly Indicate Current Participants
• Control SC-6 — Resource Availability
• Control SC-39(2) — Separate Execution Domain Per Thread
• Control SC-12(2) — Symmetric Keys
• Control SC-7(20) — Dynamic Isolation And Segregation
• Control SC-13 — Cryptographic Protection

References

• NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5
• Catalogue identifier: Control SC-23(3)

Topics: governance riskpolicy management