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Re: Blocking WMF Files via Squid
From: "Robert J. Stull" <Stull_Robert_J () cat com>
Date: Tue, 3 Jan 2006 13:18:19 -0500





I think this is a good idea, but  it is not only *.wmf extensions that have
this vulnerability, it is all files that have windows metafile headers that
will open with the Windows Picture and Fax Viewer. As long as your AV is
up-to-date you should be fine, however, it's not as fun, nor educational,
as what you did. What would be nice is if their was a way to filter these
type of headers.

Their was an email to bugtraq (Arian Evans) explaining in detail this
exploit, if anyone wants it I can forward it to the group, I just don't
want to repeat it if everyone has already read it.




R. James Stull
Network Administrator
Email - stullrj () cat com


                                                                           
             "Gaddis, Jeremy                                               
             L."                                                           
             <jeremy () linuxwiz                                              
             net>                                                       To 
                                                                        To 
             12/29/2005 10:17          Security Basics List                
             PM                        <security-basics () securityfocus com> 
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                                                                   Subject 
                                       Blocking WMF Files via Squid        
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           



Caterpillar: Confidential Green                 Retain Until: 02/02/2006
                                                Retention Category:  G90 -
                                                General
                                                Matters/Administration


In response to the new 0-day WMF exploit, the educational institution
for which I work recently took two steps to mitigate a possible infection.

The first step was filtering files with the ".wmf" extension at the
e-mail gateway via McAfee's Groupshield.  The other step was to block
URLs ending in ".wmf" through Squid, the caching proxy server (through
which all of our HTTP traffic is transparently proxied).

I have detailed the few steps that were needed to do this at
http://www.jeremygaddis.com/2005/12/29/blocking-wmf-at-the-perimeter/
in the event that it might be useful for others looking to do the same.

Please feel free to comment or provide feedback that may be of benefit.

Thanks,
-j

--
Jeremy L. Gaddis, GCWN, Linux+, Network+
http://www.jeremygaddis.com/

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---------------------------------------------------------------------------
EARN A MASTER OF SCIENCE IN INFORMATION ASSURANCE - ONLINE
The Norwich University program offers unparalleled Infosec management 
education and the case study affords you unmatched consulting experience. 
Tailor your education to your own professional goals with degree 
customizations including Emergency Management, Business Continuity Planning, 
Computer Emergency Response Teams, and Digital Investigations. 

http://www.msia.norwich.edu/secfocus
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