Home page logo

bugtraq logo Bugtraq mailing list archives

Re: recursive DNS servers DDoS as a growing DDoS problem
From: Anton Ivanov <arivanov () sigsegv cx>
Date: Tue, 04 Apr 2006 07:59:58 +0100

Geo. wrote:

1. Resolvers and Authoritative nameservers must be separate and
authoritative nameservers must have recursion turned off. Otherwise
there is no way to throttle only recursive queries.

Great, for small ISP's you just doubled the number of machines they need to
dedicate to DNS.

Not really.

    If the ISP admin has a clue he would be running two processes off
different alias addresses (best of all loopback aliases). This approach
is described in most papers on DNS admin and best practice.

    Otherwise, you are correct for the case where the admin is
illiterate and cannot read or does not bother reading. He/she will need
two machines indeed.


2. In a smaller ISP the nameservers themselves can get an aggregate of
the ISP routing table and have internal routes tagged accordingly so
that the DNS server can throttle them. No rocket science there, the
provisions are already available in every single OS in use as a DNS
server in ISPs/Telcos. All this requires is a moderate level of
competence in the person who has designed the service.

Really? Ok educate me, how do you do this with Windows 2000 running MS dns?
(telling people to use another server is not acceptable)

In an ISP or Telco?

Not acceptable - well not really... ;-)

Not realistic - hell yeah...

In any case in an ISP there will be a cisco (or equivalent) in front of
it where the same can be achieved in 5-10 lines worh of config.



A. R. Ivanov
E-mail:  aivanov () sigsegv cx
WWW:     http://www.sigsegv.cx/
pub 1024D/DDE5E715 2002-03-03 Anton R. Ivanov <ai1-n () sigsegv cx>
    Fingerprint: C824 CBD7 EE4B D7F8 5331  89D5 FCDA 572E DDE5 E715


  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]