NIST NTP servers

Joe Klein jsklein at
Wed May 11 04:05:31 UTC 2016

Is this group aware of the incident with & on November 19. 2012 2107 UTC, when the systems lost 12
years for the period of one hour, then return?

The reasons were not fully explained, but the impact was global. Routers,
switches, power grids, phone systems, certificates, encryption, Kerberos,
logging and any tightly coupled transaction systems were impacted.

So I began doing 'security research' on the topic (don't confuse me with
joe hacker), and discovered both interesting and terrifying issues, which I
will not disclose on an open forum.

Needless to say, my suggestions are:
1. Configure a trusted time source and good time stratum architecture for
your organization.
2. When identifying your source of time, the majority of the technologies
can be DDOS'ed, spoofed or MITM, so consider using redundant sources and
3. For distribution of time information inside your organization, ensure
your critical systems (Encryption, PKI, transactions, etc) are using your
redundant sources and authentication.
4. Operating systems, programming languages, libraries, and applications
are sensitive to time changes and can fail in unexpected ways. Test them
before it's too late.
5. Disallow internal system to seek NTP from other sources beyond your edge
6. All core time systems should be monitored by your security team or SOC.

One question, is this a topic anyone would find interested at a future
NANOG? Something like "Hacking and Defending time?".

Joe Klein
"Inveniam viam aut faciam"

PGP Fingerprint: 295E 2691 F377 C87D 2841 00C1 4174 FEDF 8ECF 0CC8

On Tue, May 10, 2016 at 9:59 PM, Mel Beckman <mel at> wrote:

> I don't pretend to know all the ways a hacker can find out what nap
> servers a company uses, but I can envision a virus that could do that once
> behind a firewall. Every ntp response lists the current reference ntp
> server in the next higher stratum. There are many ways that process could
> harvest all ntp servers over time, and then pass the public IP back to a
> mother ship controller. It could be going on right now.
> My point is, when the fix is so cheap, why put up with this risk at all?
>  -mel beckman
> > On May 10, 2016, at 5:18 PM, Chris Adams <cma at> wrote:
> >
> > Once upon a time, Mel Beckman <mel at> said:
> >> Boss: So how did a hacker get in and crash our accounting server, break
> our VPNs, and kill our network performance?
> >>
> >> IT guy: He changed our clocks.
> >
> > So, this has been repeated several times (with how bad things will go if
> > your clocks get changed by years).  It isn't that easy.
> >
> > First, out of the box, if you use the public pool servers (default
> > config), you'll typically get 4 random (more or less) servers from the
> > pool.  There are a bunch, so Joe Random Hacker isn't going to have a
> > high chance of guessing the servers your system is using.
> >
> > Second, he'd have to guess at least three to "win".
> >
> > Third, at best, he'd only be able to change your clocks a little; the
> > common software won't step the clock more than IIRC 15 minutes.  Yes,
> > that can cause problems, but not the catastrophes of years in the future
> > or Jan 1, 1970 mentioned in this thread.
> >
> > Is it possible to cause problems?  Yes.  Is it a practical attack?  I'm
> > not so sure, and I haven't seen proof to the contrary.
> > --
> > Chris Adams <cma at>

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