NixOS must, for networked systems, compare internal information system clocks at least every 24 hours with a server which is synchronized to one of the redundant United States Naval Observatory (USNO) time servers, or a time server designated for the appropriate DOD network (NIPRNet/SIPRNet), and/or the Global Positioning System (GPS).

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-268149	SRG-OS-000355-GPOS-00143	ANIX-00-001420	SV-268149r1039335_rule	2024-10-25	1

Description
Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate. Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network. Organizations should consider endpoints that may not have regular access to the authoritative time server (e.g., mobile, teleworking, and tactical endpoints). Satisfies: SRG-OS-000355-GPOS-00143, SRG-OS-000359-GPOS-00146, SRG-OS-000785-GPOS-00250

Description

Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate. Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network. Organizations should consider endpoints that may not have regular access to the authoritative time server (e.g., mobile, teleworking, and tactical endpoints). Satisfies: SRG-OS-000355-GPOS-00143, SRG-OS-000359-GPOS-00146, SRG-OS-000785-GPOS-00250

ℹ️ Check
Verify NixOS is configured with an approved time server with the following command: $ timedatectl show-timesync \| grep NTPServers SystemNTPServers=tick.usnogps.navy.mil FallbackNTPServers=tock.usnogps.navy.mil If the output of the command does not list authorized time servers, this is a finding.

✔️ Fix
Configure /etc/nixos/configuration.nix to use approved timeservers by adding the following configuration settings: networking.timeServers = [ "tick.usnogps.navy.mil" "tock.usnogps.navy.mil" ]; Rebuild the system with the following command: $ sudo nixos-rebuild switch