NIST 800-53 REV 5 • AUDIT AND ACCOUNTABILITY
AU-8(1) — Synchronization with Authoritative Time Source
CMMC Practice Mapping
No direct CMMC mapping
NIST 800-171 Mapping
No direct NIST 800-171 mapping
Related Controls
No related controls listed
Practitioner Notes
Synchronize with an authoritative time source — meaning a trusted, accurate reference like NIST, GPS, or a stratum-1 NTP server. Your clocks should all agree.
Example 1: Configure your primary domain controller (the one holding the PDC Emulator FSMO role) to sync with time.nist.gov or us.pool.ntp.org. Run: w32tm /config /manualpeerlist:"time.nist.gov" /syncfromflags:MANUAL /reliable:YES /update. All other domain members automatically sync from the DC hierarchy.
Example 2: For air-gapped or isolated networks, deploy a GPS-based NTP server (like a Meinberg or Microsemi appliance). The GPS receiver provides stratum-1 time accuracy without needing internet access. Configure all systems on the isolated network to sync from this local GPS time server.