r6 - 2004-10-12 - 03:02:13 - SteveKosteckeYou are here: NTP >  Support Web > NTPAccessPolicy
NTP users are strongly urged to take immediate action to ensure that their NTP daemons are not susceptible to use in a distributed denial-of-service (DDoS) attack. Please also take this opportunity to defeat denial-of-service attacks by implementing ingress and Egress filtering through BCP38.

The final two security bugs reported by Google's Security Team have been fixed as of ntp-4.2.8p1.

A new set of mode 6 vulnerabilities has been discovered and, while these vulnerabilities can be reduced by making sure you have restrict default noquery in your ntp.conf file, the best and most complete way to avoid these vulnerabilities is to install and deploy ntp-4.2.8p1 which was released on 04 February 2015.

Please see the NTP Security Notice for vulnerability and mitigation details.

Are you using Autokey in production? If so, please contact Harlan - he's got some questions for you.
REFACTOR See NTPAccessPolicyDev for discussion of this topic.

5.1. NTP Access Policy

It was proposed on news://comp.protocols.time.ntp to publish the access policy for ntp via ntp/tcp. Since ntp (the time protocol) only uses ntp/udp, ntp/tcp is available as a reserved port number for ntp.

It would be possible to publish both a machine readable version (in some standard format, to be determined) and a human readable version.

A simple solution is to use inetd to offer a file on connection to ntp/tcp. Example line in inetd.conf:

ntp  stream  tcp     nowait  nobody  /usr/libexec/tcpd       /bin/cat /etc/ntp-access-policy.txt

The file /etc/ntp-access-policy.txt would then contain the access policy.

-- KoosVanDenHout - 28 Aug 2003

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