-----Original Message-----
From: NANOG [mailto:nanog-bounces@nanog.org] On Behalf Of Leo Bicknell Sent: Wednesday, May 11, 2016 9:31 AM To: nanog@nanog.org Subject: Re: NIST NTP servers
Personally, my network gets NTP from 14 stratum 1 sources right now. You, and the hacker, do not know which ones. You have to guess at least 8 to get me to move to your "hacked" time. Good luck.
Redundancy is the solution, not a new single point of failure. GPS can be part of the redundancy, not a sole solution.
This seems like the most reasonable advise. If this truly becomes a concern, I would think IPS vendors could implement signatures to look for bad time. Lots of ways to do this - look for a difference between the IPS realtime and NTP status versus the incoming packets. - look for duplicate NTP responses, or responses that weren't requested - duplicate responses, but with differing TTLs, which might hint at one being spoofed. Chuck