GEN000240 - The system clock must be synchronized to an authoritative DoD time source - 'NTP daemon uses approved sources'
To assure the accuracy of the system clock, it must be synchronized with an authoritative time source within DoD. Many system functions, including time-based login and activity restrictions, automated reports, system logs, and audit records, depend on an accurate system clock. If there is no confidence in the correctness of the system clock, time-based functions may not operate as intended and records may be of diminished value. Authoritative time sources include authorized time servers within the enclave synchronizing with upstream authoritative sources. Specific requirements for the upstream synchronization of Network Time Protocol (NTP) servers are covered in the Network Other Devices STIG. For systems located on isolated or closed networks, it is not necessary to synchronize with a global authoritative time source. If a global authoritative time source is not available to systems on an isolated network, a local authoritative time source must be established on this network and used by the systems connected to this network. This is necessary to provide the ability to correlate events and allow for the correct operation of time-dependent protocols between systems on the isolated network. If the system is completely isolated (no connections to networks or other systems), time synchronization is not required as no correlation of events between systems will be necessary. If the system is completely isolated, this requirement is not applicable. Update NTP_SERVER_1 to the appropriate value for the local environment
Use a local authoritative time server that synchronizes to an authorized DoD time source. Ensure all systems in the facility feed from one or more local time servers feeding from the authoritative time server. View the (x)ntp/(x)ntpd man page(s). # man xntpd Create/edit the /etc/ntp.conf file, delete any non-local and/or non-US/DoD sources and insert the local or an authoritative US/DoD source. Start or restart the NTP service. # refresh -s xntpd OR # stopsrc -s xntpd # startsrc -s xntpd