The Ubuntu operating system must compare internal information system clocks at least every 24 hours with a server which is synchronized to an authoritative time source, such as the 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).

From Canonical Ubuntu 16.04 Security Technical Implementation Guide

Associated with: CCI-001891

SV-90493r2_rule The Ubuntu operating system must compare internal information system clocks at least every 24 hours with a server which is synchronized to an authoritative time source, such as the 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).

Vulnerability discussion

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).

Check content

The system clock must be configured to compare the system clock at least every 24 hours to the authoritative time source. Note: If the system is not networked this item is Not Applicable. Check the value of "maxpoll" in the "/etc/ntp.conf" file with the following command: # sudo grep -i maxpoll /etc/ntp.conf maxpoll = 17 If "maxpoll" is not set to "17" or does not exist, this is a finding. Verify that the "ntp.conf" file is configured to an authoritative DoD time source by running the following command: # grep -i server /etc/ntp.conf server 0.us.pool.ntp.org iburst If the parameter "server" is not set, is not set to an authoritative DoD time source, or is commented out, this is a finding.

Fix text

Note: If the system is not networked this item is Not Applicable. To configure the system clock to compare the system clock at least every 24 hours to the authoritative time source, edit the "/etc/ntp.conf" file. Add or correct the following lines, by replacing "[source]" in the following line with an authoritative DoD time source. maxpoll = 17 server [source] iburst If the "NTP" service was running and the value of "maxpoll" or "server" was updated then the service must be restarted using the following command: # sudo systemctl restart ntp.service If the "NTP" service was not running then it must be started.

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