Re: What are these Google IPs hammering on my DNS server?

[Damian Menscher via NANOG <nanog () nanog org>]

Google Public DNS (8.8.8.8) attempts to identify and filter abuse, and
while we think we're fairly effective for large attacks (eg, those above
1Mpps), it gets more challenging (due to risk of false positives) to
adequately filter small attacks.  I should note that we generally see the
attack traffic coming from botnets, or forwarding resolvers that blend the
attack traffic with legitimate traffic.

Based on ISC BIND load-tests [0], a single DNS server can handle O(1Mpps).
Also, no domain should be served by a single DNS server, so O(1Mpps) seems
like a safe lower-bound for small administrative domains (larger ones will
have more redundancy/capacity).  Based on these estimates, we haven't
treated mitigation of small attacks as a high priority.  If O(25Kpps)
attacks are causing real problems for the community, I'd appreciate that
feedback and some hints as to why your experience differs from the ISC BIND
load-tests.  With a better understanding of the pain-points, we may be able
to improve our filtering a bit, though I suspect we're nearing the limits
of what is attainable.

Since it was mentioned up-thread, I'd caution against dropping queries from
likely-legitimate recursives, as that will lead to a retry storm that you
won't like (based on a few reports of authoritatives who suffered outages,
the retry storm increased demand by 30x and they initially misdiagnosed the
root cause as a DDoS).  The technically correct (if not entirely practical)
mitigation for a DNS cache-busting attack laundered through open recursives
is to deploy DNSSEC and issue NSEC/NSEC3 responses to allow the recursives
to cache the non-existence of the randomized labels.

[0] https://www.isc.org/blogs/bind-performance-september-2023/

Damian
-- 
Damian Menscher :: Security Reliability Engineer :: Google :: AS15169

On Sun, Dec 3, 2023 at 1:22 PM Michael Hare via NANOG <nanog () nanog org>
wrote:

> John-
>
> This is little consolation, but at AS3128, I see the same thing to our
> downstream at times, claiming to come from both 13335 and 15169 often
> simultaneously at the tune of 25Kpps , "assuming it's not spoofed", which
> is pragmatically impossible to prove for me given our indirect
> relationships with these companies.  When I see these events, I typically
> also see a wide variety of country codes participating simultaneously.
> Again, assuming it's not spoofed.  To me it just looks like effective
> harassment with 13335/15169 helping out.  I pine for the internet of the
> 1990s.
>
> Recent events in GMT for us were the following, curious if you see the same
> ~ Nov 26 05:40
> ~ Nov 30 00:40
> ~ Nov 30 05:55
>
> Application agnostic, on the low $ end for "fixes", if it's either do
> something or face an outage, I've found some utility in short term
> automated DSCP coloring on ingress paired with light touch policing as
> close to the end host as possible, which at least keeps things mostly
> working during times of conformance.  Cheap/fast and working ... most of
> the time.  Definitely not great or complete at all, and a role I'd rather
> not play as an educational ISP/enterprise.
>
> So what are most folks doing to survive crap like this?  Nothing/waiting
> it out?  Oursourcing DNS?  Scrubbing appliance?  Poormans stuff like I
> mention above?
>
> -Michael
>
> > -----Original Message-----
> > From: NANOG <nanog-bounces+michael.hare=wisc.edu () nanog org> On
> > Behalf Of John R. Levine
> > Sent: Sunday, December 3, 2023 1:18 PM
> > To: Peter Potvin <peter.potvin () accuristechnologies ca>
> > Cc: nanog () nanog org
> > Subject: Re: What are these Google IPs hammering on my DNS server?
> >
> > > Did a bit of digging on Google's developer site and came across this:
> > > https://developers.google.com/speed/public-
> > dns/faq#locations_of_ip_address_ranges_google_public_dns_uses_to_send_
> > queries
> > > Looks like the IPs you mentioned belong to Google's public DNS resolver
> > > based on that list on their site. They could also be spoofed though
> from a
> > > DNS AMP attack, so keep that in mind.
> >
> > Per my recent message, the replies are tiny so if it's an amplification
> > attack, it's a very incompetent one.  The queries are case randomized so
> I
> > guess it's really Google.  Sigh.
> >
> > If anyone is wondering, I have a passive aggressive countermeasure
> against
> > some overqueriers that returns ten NS referral names, and then 25 random
> > IP addresses for each of those names, but I don't do that to Google.
> >
> > R's,
> > John
> >
> > >
> ------------------------------------------------------------------------------
> > > *Accuris Technologies Ltd.*
> > >
> > >
> > > On Sun, Dec 3, 2023 at 1:51 PM John Levine <johnl () iecc com> wrote:
> > >
> > > > At contacts.abuse.net, I have a little stunt DNS server that provides
> > > > domain contact info, e.g.:
> > > >
> > > > $ host -t txt comcast.net.contacts.abuse.net
> > > > comcast.net.contacts.abuse.net descriptive text "abuse () comcast net"
> > > >
> > > > $ host -t hinfo comcast.net.contacts.abuse.net
> > > > comcast.net.contacts.abuse.net host information "lookup" "comcast.net
> "
> > > > Every once in a while someone decides to look up every domain in the
> > > > world and DoS'es it until I update my packet filters. This week it's
> > > > been this set of IPs that belong to Google. I don't think they're
> > > > 8.8.8.8. Any idea what they are? Random Google Cloud customers? A
> > > > secret DNS mapping project?
> > > >
> > > >  172.253.1.133
> > > >  172.253.206.36
> > > >  172.253.1.130
> > > >  172.253.206.37
> > > >  172.253.13.196
> > > >  172.253.255.36
> > > >  172.253.13.197
> > > >  172.253.1.131
> > > >  172.253.255.35
> > > >  172.253.255.37
> > > >  172.253.1.132
> > > >  172.253.13.193
> > > >  172.253.1.129
> > > >  172.253.255.33
> > > >  172.253.206.35
> > > >  172.253.255.34
> > > >  172.253.206.33
> > > >  172.253.206.34
> > > >  172.253.13.194
> > > >  172.253.13.195
> > > >  172.71.125.63
> > > >  172.71.117.60
> > > >  172.71.133.51
> > > >
> > > > R's,
> > > > John
> >
> > Regards,
> > John Levine, johnl () taugh com, Primary Perpetrator of "The Internet for
> > Dummies",
> > Please consider the environment before reading this e-mail.
> https://jl.ly