r2 - 2008-08-30 - 01:40:36 - HarlanStennYou are here: NTP >  Dev Web > DevelopmentIssues > NtpdsSyncStatus
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.

The Synchronization Status of ntpd

There is a need to be able to easily and consistently determine if system clock and/or ntpd 's idea of its internal state and the system clock are "correct" (for some definition of correct).

To offer this ability, it seems to me that the first thing we need to nail down is the definition and specification of "correct".

The definition of 'correct' time

How about the following:

  • The decoded system status bits contain sync_ntp
  • (obsolete) ntpd is in state S_SYNC (which Dave is renaming to EVNT_SYNC)
  • any slew adjustment in-process is under X (where X is configurable)

  • Do we care about the root dispersion?
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