[dns-operations] Lot's of TXT queries from Google

Wessels, Duane dwessels at verisign.com
Thu Oct 7 14:53:36 UTC 2021


Moritz,

I can't explain the TXT queries, but the NS queries seem to be Google's method of doing qname minimization, with an added nonce value.  See https://indico.dns-oarc.net/event/39/contributions/864/ and https://developers.google.com/speed/public-dns/docs/security?hl=en#nonce_prefixes

DW


> On Oct 7, 2021, at 4:50 AM, Moritz Müller via dns-operations <dns-operations at dns-oarc.net> wrote:
> 
> 
> From: Moritz Müller <moritz.muller at sidn.nl>
> Subject: Lot's of TXT queries from Google
> Date: October 7, 2021 at 4:50:21 AM PDT
> To: <dns-operations at lists.dns-oarc.net>
> 
> 
> Hi,
> 
> For the second time in a few weeks we noticed a significant increase in queries for NS and TXT records at our .nl name servers, originating almost exclusively from the Public DNS resolvers of Google
> Did someone else noticed something similar or has an explanation?
> 
> In comparison to beginning of September, the number of NS queries increased 2 fold and the number of TXT queries almost 6 fold.
> At some point, 25% of all queries to our name servers for .nl where for TXT record.
> 
> The resolvers query either for a domain name following the pattern _dmarc.foo.nl or default._domainkey.foo.nl.
> Where foo is a random string, 12 characters long.
> 
> Examples are:
> _dmarc.mdvlxtagogij.nl.
> default._domainkey.vppj4svmbclt.nl.
> 
> The queried second level domain names are not registered and queries for the same domain name are repeated 3 to 5 times.
> At some point, 80% of all TXT queries from google had these patterns, 36% of all queries from Google resolvers.
> 
> The queries started ramping up around 2021-09-05 and reached their peak at 2021-09-18. They never reached a concerning level, but we first noticed them because our machine processing the incoming PCAP files couldn’t cope anymore.
> 
> We assume that this is likely not an attack but some tests/measurements, which got a bit out of hand. But since we don’t see the origin of the queries behind the Google resolvers, we’re not sure to whom to reach out.
> 
>> Moritz
> 
>> SIDN | Meander 501 | 6825 MD | Postbus 5022 | 6802 EA | ARNHEM
> T +31 (0)26 352 55 00
> moritz.muller at sidn.nl | www.sidn.nl
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> 
> 
> 
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