2.2.1.2 Ensure ntp is configured - restrict -4

Information

ntp is a daemon which implements the Network Time Protocol (NTP). It is designed to
synchronize system clocks across a variety of systems and use a source that is highly
accurate. More information on NTP can be found at http://www.ntp.org. ntp can be
configured to be a client and/or a server.

This recommendation only applies if ntp is in use on the system.

Rationale:

If ntp is in use on the system proper configuration is vital to ensuring time synchronization
is working properly.

Solution

Add or edit restrict lines in /etc/ntp.conf to match the following:

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

Add or edit server or pool lines to /etc/ntp.conf as appropriate:

server <remote-server>

Configure ntp to run as the ntp user by adding or editing one of the following files as
appropriate for your distribution:
/etc/sysconfig/ntpd :

OPTIONS="-u ntp:ntp"

/etc/sysconfig/ntp :

NTPD_OPTIONS="-u ntp:ntp"

/etc/init.d/ntp:

RUNASUSER=ntp

See Also

https://workbench.cisecurity.org/files/2420

Item Details

Category: AUDIT AND ACCOUNTABILITY

References: 800-53|AU-8, CSCv6|6.1, CSCv7|6.1

Plugin: Unix

Control ID: ab45175b8cc8bb50601c6b570e19fd31eb652e1a81a49e403bdc82bf67d0dd79