full-disclosure - Re: recursive DNS servers DDoS as a growing DDoSproblem

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Message-ID: <E9687DBE2FCDA64BA77282F7E36BADBC030EEC90@mail.terradon.com>
Date: Tue Mar 14 04:23:30 2006
From: keith.morgan at terradon.com (Keith T. Morgan)
Subject: Re: recursive DNS servers DDoS as a growing
	DDoSproblem

FWIW, we've seen the exact activity you outline below in the wild.   In
this case, it was associated with spam.

-----Original Message-----
From: Geo. [mailto:geoincidents@....net] 
Sent: Wednesday, March 08, 2006 1:27 PM
To: bugtraq@...urityfocus.com
Cc: full-disclosure@...ts.grok.org.uk
Subject: RE: [Full-disclosure] Re: recursive DNS servers DDoS as a
growing DDoSproblem

>>In the scenario you describe, I cannot see any actual amplification...

I'll give you a senario where you can see.

lets say you have 2 name servers that are local to you.

I setup a domain, example.com. In this domain I create a text record
which is 100K in length, I don't know, perhaps I paste the source code
to decss in it, whatever it's a big text record.

Now I simply spoof a UDP packet using your IP address as the source
address and send it to both of your dns servers. This packet is a query
for the example.com text record. I have now sent two very small packets
and you have received 200K of traffic. That's the amplification, one
small udp packet, one large text record in return.

Note, I don't have to use your local servers, but this way it makes it
more fun to troubleshoot because it looks like you are the cause of your
own flooding..

Geo.
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