NIST SP 800-53 Rev. 5 SC-45 — System Time Synchronization

What this control requires

Synchronize system clocks across all systems and components to ensure proper execution of services like authentication, certificate verification, and time-based access control. Inconsistent or unsynchronized clocks may lead to failures such as denial of service or improper handling of expired credentials. Systems should adhere to standardized time protocols such as Coordinated Universal Time (UTC) or local time with UTC offsets, with synchronization granularity depending on system requirements. This control supports the Security operations, access control, system reliability capability within the System and Communications Protection family.

In plain English

Synchronize system clocks across all systems and components to ensure proper execution of services like authentication, certificate verification, and time-based access control. In practice, this means you can prove you access 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 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 System and Communications Protection, the assessor will trace your implementation back to the catalogue reference (Control SC-45) and look for objective evidence on the latest two assessment cycles.

How to implement

1. Write a short policy stating intent, scope and named owner.
2. Encode it as a platform guardrail — SCP, Azure Policy initiative, Organisation Policy, or repository policy.
3. Wire a monitoring signal that catches drift (CSPM rule, SIEM rule, scheduled query, Workspace alert) and ticket it.
4. Review on a documented cadence and capture the review in the risk register or compliance tracker.

Operational checklist

• Access. Document the trigger, the owner and the cadence.
• Security. Document the trigger, the owner and the cadence.
• Review. Document the trigger, the owner and the cadence.
• Protection. Document the trigger, the owner and the cadence.
• Authentication. Document the trigger, the owner and the cadence.
• Scope: management, access control, authentication, system, service, time, protection, identity.

Evidence to collect

• Identity Scan. IAM / IdP exports — Entra ID, Okta, IAM Identity Center, Workspace directory — showing accounts, roles, MFA state and last sign-in.

Identity analytics (Okta, SailPoint, Access Analyzer) demonstrates least-privilege. Focus: System Time Synchronization.

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.

• CIS Controls v8 6.7 — Centralize Access Control
• NIST SP 800-171 Rev. 3 3.15.2 — System Security Plan

Related controls in NIST SP 800-53 Rev. 5

• Control AC-11 — Device Lock
• Control SC-7(3) — Access Points
• Control AC-14 — Permitted Actions Without Identification Or Authentication
• Control SC-20 — Secure Name/Address Resolution Service (Authoritative Source)
• Control PE-3(1) — System Access
• Control PE-8(1) — Automated Records Maintenance And Review

References

• NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5
• Catalogue identifier: Control SC-45

Topics: identity accessidentity managementaccess reviewprivileged accesscertificate management