SC-45: System Time Synchronization

SC-45 requires you to synchronize clocks across your systems and components so security logs, authentication events, backups, and incident timelines align reliably. To operationalize it fast, standardize on an approved time source, enforce time sync on all in-scope assets, monitor drift, and retain evidence that time synchronization is configured and working in production. ¹

Key takeaways:

• Pick authoritative time sources and make them the standard for every in-scope system. ¹
• Enforce and monitor clock sync across endpoints, servers, network gear, and cloud workloads; investigate drift as an incident precursor. ¹
• Keep assessor-ready evidence: configurations, inventory-to-time-source mapping, monitoring outputs, and change records. ¹

The sc-45: system time synchronization requirement is easy to underestimate because “time” feels like a basic IT setting. In audits and incident response, it becomes a hard dependency: if system clocks disagree, log correlation breaks, detection rules misfire, forensics timelines become disputable, and you lose confidence in what happened and when.

SC-45 is a straightforward control statement with operational bite. You must synchronize clocks “within and between systems and system components.” ¹ That includes workloads that never touch your corporate network, assets owned by third parties but operated on your behalf, and managed services where you only control configuration through a console or contract.

This page is written for a Compliance Officer, CCO, or GRC lead who needs to assign ownership, define the required implementation, and collect evidence that stands up to an assessor. The goal is to get you from requirement text to a working, monitored, and documentable control with minimal churn.

Regulatory text

Requirement (verbatim): “Synchronize system clocks within and between systems and system components.” ¹

Operator meaning: You need a consistent time baseline across your environment so events recorded by one component can be accurately compared to events recorded by another component. Treat this as an engineering standard plus an assurance activity: (1) configure time synchronization everywhere, (2) verify it stays in sync, and (3) prove it with repeatable evidence. ¹

Plain-English interpretation

SC-45 expects that:

• Every in-scope system gets its time from an approved, consistent time source.
• Components do not “free-run” on local clocks without correction.
• You can detect and correct time drift before it creates security and operational errors.
• You can demonstrate the control in an assessment with artifacts tied to your asset inventory. ¹

If you can’t answer “what is the time source for this system?” quickly and consistently, you are not operationalizing SC-45.

Who it applies to

Entities: Federal information systems and contractor systems handling federal data are explicitly in scope for NIST SP 800-53 alignment programs. ¹

Operational contexts that routinely fall into scope:

• Centralized identity and security tooling (IdP, SIEM, EDR, SOAR), where event ordering matters.
• Systems producing security-relevant logs (applications, databases, OS logs, WAF, network devices).
• Distributed systems and microservices, where cross-service tracing depends on consistent timestamps.
• Virtualized and cloud infrastructure, where “host time” and “guest time” can diverge if not managed.
• Third party managed platforms where you still have compliance responsibility (contract and evidence become key).

What you actually need to do (step-by-step)

1) Assign ownership and define the standard

1. Name a control owner (often Infrastructure/SRE or Security Engineering) and a GRC point person accountable for evidence quality.
2. Define the “approved time sources” you will allow (example: enterprise NTP hierarchy, cloud-provider time sync service if approved internally).
3. Define the scope using your system boundary: production, staging if it feeds production telemetry, and all security tooling that produces or stores logs.
4. Document the standard in a short “Time Synchronization Standard” that states: allowed sources, required configuration, drift alert thresholds (your choice), and exceptions process. ¹

Practical note: auditors rarely want your preferred NTP vendor. They want a clear, consistently applied approach.

2) Build an asset-to-time-source map

1. Export your authoritative inventory (CMDB, cloud asset inventory, endpoint management list).
2. For each asset class, record the expected time method and upstream source:
   • Windows endpoints/servers: domain time hierarchy or approved NTP
   • Linux servers: chrony/ntpd config pointing to approved sources
   • Network devices: NTP servers configured, authenticated if your standard requires it
   • Containers/Kubernetes: node time sync plus cluster guidance for workloads that stamp events
   • Cloud services (managed databases, load balancers): provider time sync behavior plus what you can configure
3. Flag “unknown time source” as a compliance defect that must be remediated or explicitly excepted. ¹

3) Enforce configuration across platforms

1. Implement via configuration management (GPO, MDM, Ansible, Puppet, Chef, Terraform/cloud policy) so time settings are not hand-tuned.
2. Lock down local overrides where feasible (admin rights, config file permissions, policy guardrails).
3. Standardize time zone handling (most orgs choose UTC for servers and security tooling). The requirement is synchronization, but time zone inconsistency creates analysis errors that look like drift.
4. Handle offline/segmented networks: define internal authoritative time sources in each enclave and document how they stay consistent with your enterprise time baseline. ¹

4) Monitor drift and alert on failures

1. Implement continuous monitoring that answers:
   • Is time sync service running?
   • What is the current offset from expected?
   • When did the last successful sync occur?
2. Send drift/failure telemetry into your central monitoring and, where relevant, SIEM.
3. Define triage playbooks:
   • Sudden drift spikes can indicate misconfiguration, VM host issues, or tampering.
   • Persistent drift is usually configuration debt or blocked NTP traffic.
4. Track drift remediation as operational work with clear closure criteria. ¹

5) Make exceptions explicit and time-bound

Some systems cannot follow the standard (legacy appliances, constrained OT, isolated lab systems). Treat this as risk acceptance with compensating controls:

• Document why sync is not possible.
• Document how logs from that system will be interpreted (for example, ingest pipeline time-stamping on receipt).
• Set a review trigger (change window, end-of-life milestone, or system replacement plan). ¹

6) Operationalize evidence collection (don’t scramble at audit time)

Run evidence collection on a cadence aligned with your assessment cycle and change velocity. The evidence must show both design (what you intended) and operation (what is happening). ¹

If you use Daydream, map SC-45 to a single control owner, a written implementation procedure, and a recurring evidence checklist so collection is consistent across systems and assessment periods. This matches the recommended control pattern: assign ownership, define procedure, and retain recurring artifacts. ¹

Required evidence and artifacts to retain

Keep artifacts that tie configuration and operation to in-scope systems:

Design / governance

• Time Synchronization Standard (approved sources, configuration expectations, exceptions process). ¹
• Control ownership record (RACI or control register entry naming accountable team). ¹
• System boundary/scope statement showing what environments are included. ¹

Implementation

• Configuration baselines (GPO exports, MDM profiles, Linux config templates, network device standards).
• IaC/policy artifacts showing time sync settings enforced in cloud and clusters.
• Asset-to-time-source mapping (spreadsheet or CMDB fields). ¹

Operational proof

• Monitoring dashboards or reports showing sync status and drift over time.
• Sample host outputs demonstrating current synchronization status across representative assets per platform.
• Tickets/incident records for time drift events with root cause and resolution.
• Change records for time source changes or policy updates. ¹

Common exam/audit questions and hangups

Expect assessors to ask questions that test both completeness and durability:

• Scope completeness: “Which systems are in scope, and how do you know every one is synchronized?”
  Hangup: inventory gaps. Fix by tying evidence sampling to inventory and showing coverage logic.

• Authoritative sources: “What are your approved time sources, and who can change them?”
  Hangup: informal, undocumented NTP servers or ad hoc per-team choices.

• Operational monitoring: “How do you detect and respond to drift or NTP failures?”
  Hangup: configuration exists, but nobody watches it.

• Cloud/managed services: “How do you address time for services you don’t administer?”
  Hangup: missing shared responsibility narrative and contract/evidence approach. ¹

Frequent implementation mistakes and how to avoid them

Mistake	Why it fails SC-45 operationally	Fix
Treating NTP as “set-and-forget”	Drift and service failures go unnoticed until an incident	Add monitoring, alerting, and ticketed remediation 1
Only synchronizing “servers,” not security tooling	SIEM correlation and detection timelines degrade	Include log collectors, auth systems, network gear, and cloud control planes in scope
No asset-to-time-source mapping	You cannot prove completeness	Maintain inventory fields or a mapping artifact tied to the boundary 1
Uncontrolled exceptions	Legacy systems become permanent holes	Require approval, compensating controls, and time-bound review 1
Time zone inconsistency	Humans misread incidents and audit evidence	Standardize on UTC for servers and security systems; document exceptions

Risk implications (why auditors care)

Unsynchronized time creates concrete control failures:

• Incident response risk: you cannot build a defensible event timeline across systems.
• Detection risk: correlation rules may mis-order events or miss sequences.
• Non-repudiation and investigation risk: authentication and privileged activity logs become harder to trust.
• Operational risk: scheduled jobs, certificates, and distributed transactions can fail or behave unpredictably.

SC-45 is a “small” control that supports many others indirectly because so many security decisions rely on timestamps. ¹

Practical 30/60/90-day execution plan

First 30 days: Establish control ownership and stop the bleeding

• Assign control owner and publish a one-page time synchronization standard. ¹
• Identify approved time sources and document where they live (on-prem, cloud, enclave).
• Build the initial asset-to-time-source map for the highest-risk systems: identity, logging, critical production workloads.
• Create an exceptions intake path and capture any known “can’t sync” systems.

Next 60 days: Enforce consistency and instrument monitoring

• Roll out enforced configuration via your platform tooling (GPO/MDM/config management/IaC).
• Expand coverage to remaining in-scope assets and close “unknown time source” gaps.
• Stand up monitoring for sync health and drift; route alerts to an on-call queue.
• Run a tabletop: “NTP failure” and validate your response and evidence outputs.

By 90 days: Prove operation and become assessment-ready

• Produce a repeatable evidence packet: configs, mapping, monitoring outputs, sample checks, and exception register. ¹
• Add a recurring control check in your GRC calendar tied to system changes (new environments, new third parties, new enclaves).
• If using Daydream, configure SC-45 as a requirement with an assigned owner, documented procedure, and recurring evidence tasks so audit prep is a routine export, not a scramble. ¹

Frequently Asked Questions

Do we need a specific NTP product to satisfy SC-45?

SC-45 does not mandate a product. You need an approved, documented time source strategy and proof that systems and components synchronize to it in operation. ¹

Are cloud-managed services “covered” if the provider handles time?

They are still part of your system boundary if they process or store in-scope data. Document the provider’s role, what you can configure, and how you validate time alignment through logs/monitoring and contractual or shared responsibility documentation. ¹

What’s the minimum evidence an assessor will accept?

Provide a written standard, an inventory-linked mapping of systems to time sources, configuration proof for representative platforms, and monitoring outputs showing synchronization is working. Tie samples back to scope. ¹

How do we handle isolated networks with no internet access?

Establish internal authoritative time sources inside the enclave and document how they remain consistent with your enterprise baseline. Then treat the enclave like any other environment for configuration and monitoring evidence. ¹

We have legacy appliances that can’t sync time. Is that an automatic failure?

It becomes an exceptions problem. Record the exception, the reason, compensating controls for log interpretation, and a plan to remediate or retire the system. Keep approvals and review records. ¹

Who should own SC-45 in practice: Security or Infrastructure?

Infrastructure/SRE typically owns implementation because it’s configuration and monitoring across platforms. Security/GRC should own the requirement mapping, evidence quality, and exception governance so the control stays assessable. ¹

Footnotes

1. NIST SP 800-53 Rev. 5 OSCAL JSON