bugtraq - Re: recursive DNS servers DDoS as a growing DDoS problem

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Date: Sun, 26 Mar 2006 11:34:53 -0500
From: "Geo." <geoincidents@....net>
To: <bugtraq@...urityfocus.com>
Subject: Re: recursive DNS servers DDoS as a growing DDoS problem

> Spoofing is indeed the attack vector and it can also be utilized for
> NTP, ICMP, etc. It is to blame.
>
> Still, DNS is what's being exploited and in my opinion a broken feature
> being exploited needs fixing, or it will be exploited.

What feature of DNS is being exploited, UDP or the fact that there are a lot
of dns servers you can use?

If you have a 20,000 bot botnet and each bot has 2 defined recursive dns
servers that it is allowed to use and these bots are on the local subnet (ie
BCP38 is implimented at the gateway but not at every router) then how
exactly is locking down recursive servers so you can only use yours going to
solve anything?

To fix DNS we would have to eliminate it's use of UDP which means pretty
much all internet software would need to be rewritten, that is an
unrealistic goal. Locking down recursive servers may increase the number of
machines required to create a flood but again a large botnet will have no
problem so that's no solution either. BCP38 will accomplish the same
ineffective goal but at least has the added potential to reduce non DNS
related spoofed attacks at the same time making it easier to at least track
down the sources of a distributed flood at least to the provider level if
not to the exact IP.

Geo.