Security Basics mailing list archives

Re: Instant Messaging hash values


From: Dave Aronson <sfbasics2dave () davearonson com>
Date: Sat, 6 Aug 2005 10:38:27 -0400

"Nick Duda" <nduda () VistaPrint com> wrote:

I'm looking to create a software restriction policy via GPO to
prevent different instant messenger services (AIM, MSN, Yahoo,
Trillian..etc) from running based on the hash value. Short of
gathering all know binaries for each client is there any way to
obtain hash codes from past versions anywhere....perhaps a website
with a repository of hash values for binaries?

All it would take to get around that, is for someone to compile it 
themselves.  Only if there's absolutely nothing in the binary that 
depends in any way on the time, or particular machine, or installed 
libraries detected, etc., will the hashes work out the same.  (Barring 
the occasional coincidental collision of course.)

Don't get too hung up on using technology to solve every problem.  How 
about prevention via deterrence: get caught running this stuff and you 
get, oh, say, something vague like "penalties to be decided in 
accordance with the severity of the case, ranging from verbal reprimand 
to immediate termination and, if applicable, required reimbursement of 
consequential damages" (like if you let in an IM-borne virus)?

-Dave


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