[unisog] Anyone got a script that will detect bad excel files?

Sergent, Phil sergent at marshall.edu
Wed Jun 21 15:18:54 GMT 2006


>From Security Focus:

Microsoft Excel Unspecified Remote Code Execution Vulnerability
http://www.securityfocus.com/bid/18422/discuss


 

Phil Sergent                      Systems  Programmer   
Marshall University  -  Computing Services - Systems
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                    Contact: sergent at marshall.edu
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Mark Twain


-----Original Message-----
From: unisog-bounces at lists.sans.org
[mailto:unisog-bounces at lists.sans.org] On Behalf Of Michael Holstein
Sent: Wednesday, June 21, 2006 9:49 AM
To: UNIversity Security Operations Group
Subject: Re: [unisog] Anyone got a script that will detect bad excel
files?

The vulnerability lies in the ability to embed an "auto-launch" program 
within the file (this was probably intended to have some cutsie flash 
thing popup when you opened a spreadsheet).

I'll play with it more later, but after doing several forensic 
recoveries of excel documents using a hex editor, all you'd need to do 
is find the field marker for that type of action and do a regex match on
it.

/mike.

PS: note that not just .xls could be infected .. among other things, 
Excel considers *.xl* to be a valid excel file)

Russell Fulton - ISO wrote:
> Hi,
> 	Like many of you we run Amavisd to do spam detection.  It has
the
> ability to start scripts under some conditions (like when there is an
> excel file as an attachment) passing the directory containing all the
> attachments to the script.  We thought that this would be a good way
of
> flagging suspect excel attachments.
> 
> Russell
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