A good way to reduce this is to turn off recursion for people not on your network for your dns server. This is fairly easy to do with bind8/bind9.
The attack isn't via recursive lookups (though recursion could help augment the attack). The reflection is in terms of the DNS reply to the purported requestor (really the victim). At lbl.gov, none of the requests result in further lookups from our nameserver. But the victim still receives the reply stream, which from a combined large number of name servers is very large. See my draft paper ftp://ftp.ee.lbl.gov/.vp-reflectors.txt for a discussion of reflector attacks. Vern
I am still curious as to why *this* attack would even exist (seeing that it uses a spoofed source IP address) if people were filtering traffic that were originationg from their networks properly. I thought we discussed this already last month on the list. Bora ----- Original Message ----- From: "Vern Paxson" <vern@ee.lbl.gov> To: "Jared Mauch" <jared@puck.Nether.net> Cc: "Steven M. Bellovin" <smb@research.att.com>; <jtk@aharp.is-net.depaul.edu>; <nanog@merit.edu> Sent: Tuesday, January 09, 2001 6:45 PM Subject: Re: DNS requests from 209.67.50.203
A good way to reduce this is to turn off recursion for people not on your network for your dns server. This is fairly easy to do with bind8/bind9.
The attack isn't via recursive lookups (though recursion could help
augment
the attack). The reflection is in terms of the DNS reply to the purported requestor (really the victim). At lbl.gov, none of the requests result in further lookups from our nameserver. But the victim still receives the reply stream, which from a combined large number of name servers is very large.
See my draft paper
ftp://ftp.ee.lbl.gov/.vp-reflectors.txt
for a discussion of reflector attacks.
Vern
participants (2)
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Bora Akyol -
Vern Paxson