Cis Ubuntu1204 V110 6 5

6.5 Configure Network Time Protocol (NTP) (Scored)

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• Level 1

Description

The Network Time Protocol (NTP) is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. NTP can be configured to be a client and/or a server.

Rationale

It is recommended that physical systems and virtual guests lacking direct access to the physical host's clock be configured as NTP clients to synchronize their clocks (especially to support time sensitive security mechanisms like Kerberos). This also ensures log files have consistent time records across the enterprise, which aids in forensic investigations.

Audit Procedure

Using Command Line

Run the following to ensure ntp is installed:

dpkg -s ntp

Check for the correct parameters on restrict default and restrict -6 default:

grep "restrict .* default" /etc/ntp.conf

Determine if the system is configured to use an NTP Server and that the ntp daemon is running as an unprivileged user:

grep "^server" /etc/ntp.conf
grep "RUNASUSER=ntp" /etc/init.d/ntp

Expected Result

• Package status is installed ok installed.
• Restrict lines show: restrict -4 default kod nomodify notrap nopeer noquery and restrict -6 default kod nomodify notrap nopeer noquery.
• At least one NTP server is configured.
• RUNASUSER=ntp is present.

Remediation

Using Command Line

Install ntp:

apt-get install ntp

Ensure the following lines are in /etc/ntp.conf:

restrict -4 default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

Also, make sure /etc/ntp.conf has at least one NTP server specified:

server <ntp-server>

Note: <ntp-server> is the IP address or hostname of a trusted time server.

Default Value

NTP is not installed by default on Ubuntu 12.04 LTS Server.

References

• CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
• http://www.ntp.org

Profile

Level 1 - Scored