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

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Message-ID: <20060404025419.GF3575@sentinelchicken.org>
Date: Mon, 3 Apr 2006 22:54:19 -0400
From: Tim <tim-security@...tinelchicken.org>
To: Anton Ivanov <arivanov@...segv.cx>
Cc: gboyce <gboyce@...belly.com>, "Geo." <geoincidents@....net>,
	bugtraq@...urityfocus.com
Subject: Re: recursive DNS servers DDoS as a growing DDoS problem

> All it takes is  to throttle traffic from the resovers to outside the
> ISP network to a reasonably low value. Depending on the ISP this is
> usually in the low Kbits. All it takes is a moderate amount of
> competence in the ISP:

I don't believe this would help the problem.  One of the notable
features of many reflected attacks is that no single reflector is hit
with a large amount of traffic.  It is spread out amongst many many
reflectors so that the reflectors don't notice the issue, and so that
the victim has a harder time filtering the traffic.

If your goal is to eliminate the recursive resolution reflection
amplification, then you must disable it for all but trusted subnets.
This also defends the server from the more trivial of cache poisoning
attacks (assuming your own systems use the resolver as well).

tim