Hello
This Mail [1] arrived just over the Full-Disclosure mailinglist [2], but should probably also be of interest to some people here.
[1] http://lists.grok.org.uk/pipermail/full-disclosure/2005-May/034342.html [2] https://lists.grok.org.uk/mailman/listinfo/full-disclosure
bye Fabian
-------- Original Message -------- Subject: [Full-disclosure] DNS Smurf revisited Date: Fri, 27 May 2005 10:28:37 -0400 From: Ian Gulliver ian-fulldisclosure@penguinhosting.net To: full-disclosure@lists.grok.org.uk
DNS smurf is old news:
http://www.s0ftpj.org/docs/spj-002-000.txt http://www.ciac.org/ciac/bulletins/j-063.shtml
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 9.55
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.
SOLUTIONS ---------
ISPs: Drop outgoing packets that don't originate from within your network. You should already be doing this, as it stops a variety of other attacks.
NS operators: Ratelimit?
Attached is a modernized proof of concept.