NIST 800-171 Control 3.3.7: Authoritative Time Source
System clock synchronization is critical for audit trails, compliance logs, and detecting security anomalies across your infrastructure. Control 3.3.7 requires you to compare and synchronize internal system clocks with a trusted authoritative source—a foundational step many organizations overlook until audit time.
What this means
Your organization must implement a system capability that automatically compares internal system clocks against an authoritative time source (such as NIST time servers or atomic clocks) and synchronizes them. This ensures all devices, servers, and applications operate on accurate, consistent time—essential for forensic analysis, log correlation, and detecting temporal attack patterns.
How to comply
- 1.Select an authoritative time source (e.g., NIST Internet Time Service, NTP pool servers, or atomic clock appliances)
- 2.Configure Network Time Protocol (NTP) or similar synchronization service on all system clocks
- 3.Set synchronization intervals to occur at least once per day, or more frequently for critical systems
- 4.Document your time source selection and validate its accuracy and availability
- 5.Test synchronization across all systems and monitor for drift or failures
- 6.Implement alerts for systems that fail to synchronize or exceed acceptable time deviation thresholds
- 7.Maintain audit logs showing successful synchronizations and any correction events
Evidence auditors look for
- NTP configuration files showing authoritative time server addresses
- Automated synchronization logs with timestamps confirming regular clock updates
- System monitoring dashboard displaying clock synchronization status across all devices
- Change management records documenting NTP server implementation and updates
- Incident response logs showing detection of time-sync failures and corrective actions
- Network traffic captures showing NTP communication to authoritative sources
- Policy documentation defining acceptable time deviation tolerances and review procedures
Frequently asked questions
When will FAQs be available?
The FAQ for this control is currently being prepared.
GRCWatch automatically monitors NTP synchronization status across your systems and collects timestamped evidence, eliminating manual clock audits and compliance gaps during assessments.
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