System Time Synchronization
LOW MODERATE HIGHRequirements NIST SOURCE
Synchronize system clocks within and between systems and system components.
Discussion (NIST Supplemental Guidance)
Time synchronization of system clocks is essential for the correct execution of many system services, including identification and authentication processes that involve certificates and time-of-day restrictions as part of access control. Denial of service or failure to deny expired credentials may result without properly synchronized clocks within and between systems and system components. Time is commonly expressed in Coordinated Universal Time (UTC), a modern continuation of Greenwich Mean Time (GMT), or local time with an offset from UTC. The granularity of time measurements refers to the degree of synchronization between system clocks and reference clocks, such as clocks synchronizing within hundreds of milliseconds or tens of milliseconds. Organizations may define different time granularities for system components. Time service can be critical to other security capabilities—such as access control and identification and authentication—depending on the nature of the mechanisms used to support the capabilities.
Enhancements NIST SOURCE
SC-45(1) Synchronization with Authoritative Time Source LOW MODERATE HIGH
- (a) Compare the internal system clocks [frequency] with [authoritative time source] ; and
- (b) Synchronize the internal system clocks to the authoritative time source when the time difference is greater than [time period].
Discussion
Synchronization of internal system clocks with an authoritative source provides uniformity of time stamps for systems with multiple system clocks and systems connected over a network.
SC-45(2) Secondary Authoritative Time Source LOW MODERATE HIGH
- (a) Identify a secondary authoritative time source that is in a different geographic region than the primary authoritative time source; and
- (b) Synchronize the internal system clocks to the secondary authoritative time source if the primary authoritative time source is unavailable.
Discussion
It may be necessary to employ geolocation information to determine that the secondary authoritative time source is in a different geographic region.
Implementation Guidance
Original engineering commentary written for this explorer — not NIST source text and not authoritative guidance.
No engineering interpretation has been authored for SC-45 yet. This section is architected to receive it — see the Requirements and Assessment sections above for the authoritative NIST source content in the meantime.
Assessment
Assessment Objectives
- system clocks are synchronized within and between systems and system components.
Examine
[SELECT FROM: System and communications protection policy; procedures addressing time synchronization; system design documentation; system configuration settings and associated documentation; system audit records; system security plan; other relevant documents or records].
Interview
[SELECT FROM: System/network administrators; organizational personnel with information security responsibilities; organizational personnel installing, configuring, and/or maintaining the system].
Test
[SELECT FROM: Mechanisms supporting and/or implementing system time synchronization].
Overlays
STIGs & CCIs
No STIG checks or CCI mappings are currently loaded for SC-45. This section is architected to display, per product: STIG ID, Finding ID, Severity, Title, Description, Check, Fix, CCI, and NIST control mapping — but nothing is populated here until a real DISA STIG/CCI dataset is ingested.
Learn more about STIG/CCI integration →Evidence
Categorized from the SP 800-53A "Examine"/"Test" artifact list above by keyword — not an authoritative NIST evidence list.
Policy
- System and communications protection policy
- system security plan
Configuration
- system design documentation
- system configuration settings and associated documentation
Testing
- Mechanisms supporting and/or implementing system time synchronization
Other Records
- procedures addressing time synchronization
- system audit records
- other relevant documents or records