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Message-ID: <BANLkTineExnvvVrN=m4D=3ocTMSx3m0rxw@mail.gmail.com>
Date: Thu, 19 May 2011 18:55:24 +0200
From: joris dedieu <joris.dedieu@...il.com>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: New DDoS attack vector
2011/5/19 minor float <minor.float@...il.com>
> Dear list readers, on today we officially published our observations
> regarding the new attack vector of the DDoS against the DNS servers.
>
> A full story can be read here http://www.zone-h.org/news/id/4739
>
> Here is the excerpt.
>
>
> The attack phases are as follows:
>
> The attacker obtains the IP address /hostname of the target DNS server.
>
> The attacker updates the NS records of the pre-registered domain foo
> -domain.com with the IP address /hostname of the target DNS
> server. Some registrars or hosting providers do not provide this
> functionality, many other do. There are known hosting companies
> and ISP that are supporting the spam [5]. After the NS records
> update the attacker waits at least 24 hours until the new records are
> propagated all over the Internet.
>
Note that it's not possible with several tld. Eg : fr nic, afinc.net (and I
hope some other)
checks that an SOA record is present (and much more. See
http://www.zonecheck.fr)
on the name server before updating NS records in the registry.
Now the attacker prepares a spam campaign. There are few aspects to
> note: as first, the sender mail address for the MAIL FROM can contain
> the same user name, but the subdomain — 3rd level domain must vary
> per each spam message (for example first spam message has the
> sender james@subdom1.foo-domain.com but the second sender has to
> be james@subdom2.foo-domain.com).
>
> The second important aspect is the selection of the white horse
> systems. White horse systems are the SMTP incoming mail servers
> with a high bandwidth.
>
> Once the spam campaign has been started to the white horse systems
> using the spam botnet, these systems check on the background
> whether the sender’s domain resolves to the domain MX or at least to
> an A record. Since the NS record is set to the target DNS server, the
> DNS requests will be performed to the target DNS server.
>
> Target DNS server receives multiple regular DNS requests for the
> bogus subdomain records(note that in the previous Denial of
> Service attacks against the DNS servers received either malformed,
> fragmented, ICMP messages or TCP SYN, with invalid length, or
> oversized and some of these can be filtered by the firewalls or
> security appliances). Since the DNS server does not have the records
> for the foo-domain.com, it has to respond negatively to the
> request. If the spam campaign is successful, the white horse
> systems flood the DNS server with multiple valid DNS requests.
>
> Regards
>
> Jakub Alimov [Seznam.cz]
> minor [zone-h.org]
>
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