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DNS Smurf revisited
From: Ian Gulliver <ian-fulldisclosure () penguinhosting net>
Date: Fri, 27 May 2005 10:28:37 -0400
DNS smurf is old news:
However, as ISPs continue to operate networks that let spoofed packets
out this issue deserves a little publicity again.
10:17:07.641061 IP (tos 0x0, ttl 64, id 46429, offset 0, flags [DF], length: 49) XXXXXXXXXXXXX.44295 >
c.gtld-servers.net.domain: [udp sum ok] 18297 ANY? org. (21)
10:17:07.673800 IP (tos 0x0, ttl 43, id 0, offset 0, flags [DF], length: 468) c.gtld-servers.net.domain >
XXXXXXXXXXXXX.44295: 18297- 0/13/13 (440)
% echo "2 k 468 49 / p" | dc
That's a 9.5X amplification of outgoing traffic; you can probably break
10X with a little more work on the query and nameserver choices.
ISPs: Drop outgoing packets that don't originate from within your
network. You should already be doing this, as it stops a variety of
NS operators: Ratelimit?
Attached is a modernized proof of concept.
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- DNS Smurf revisited Ian Gulliver (May 27)