Re: FAX virus

[Alcides <alcides.hercules () gmail com>]

Hi List,
Kindly find the original security-basics post below. Many people tried 
to help with their precious opinions and technical aspects.

This thread was closed by moderator of security basics list because 
several reasons.
http://seclists.org/basics/2007/Mar/0075.html 
<http://seclists.org/basics/2007/Mar/0000.html>
This matter has now an additional aspect and a reason to reopen this 
thread here.

Zero day PDF exploit for Adobe Acrobat is in the wild for sometime, poc is also available.

So, do we need to rethink about what bad guys can do to my windows box. Which is acting as FAX server with some software of 
"make-my-computer-a-fax-machine" type.
Kindly discuss about the various attack vectors, and ways to safeguard against the same.

Thanks and regards,
Alcides



> From: Alcides <alcides.hercules_at_gmail.com 
> <mailto:alcides.hercules_at_gmail.com?Subject=Re:%20FAX%20a%20virus>>
> Date: Thu, 01 Mar 2007 10:07:19 +0530
>
> Hi lists,
> My FAX server allows me to receive faxes from my clients from Internet.
> My clients send me some documents using their built-in Fax Printer on
> their PC. My fax server routes the stuff to the document processing
> applications. The document processing system extracts various data
> fields from received portable document format files.
> The whole scenario is windows environment and let's assume that virus
> protection is temporarily off.
>
> Now, I have a query:
> Can anyone send a fax that includes a file infected with the virus/ worm
> operates as a VBS script embedded within a PDF/TIF file to cause
> infections to my computers/ to affect my FAX system?
> What about other possibilities of "the bad guys" using some joiner (or
> wrapper as some say) to bind malware (trojan server etc) with the pdf/
> TIF files and fax it to me?
> I would be very greatful to know what are the various possibilities.
>
> Warm regards,
> Alcides.
>
> --------------------------------------------------------------------------- 


cwright () bdosyd com au wrote:
> Scott,
>
> The question was originally posed as “Can anyone send a fax that includes a file infected with the virus/ worm” (Wed, 
> 07 Mar)
>
> My concern was not with sanitisation as you are trying to suggest. It is with the idea that a buffer overflow is the attack vector. That for instance a virus / worm could be embedded. This is a suggestion that I remain in disbelief of. 
>
> What I suggested is an alternative. Rather then sending  a virus/worm, send a XSS attack and rely on the users in the 
> organisation to exploit this.
>
> If this is sent in a PDF, it is going to display as the scripted entry. So a conversion to an attached PDF is still not 
> going to work as what is displayed is what is on the page. It will need to be sent directly to a web enabled email or 
> web server.
>
> So it is not that I am suggesting an attack against the document processor, but rather extending this by adding user 
> interaction. It is thus the user who extends this through reading email with the link or opening a page. In this case 
> the site would still also have a simpler attack against the user in any instance.
>
> I also believe that you suggested “If you allow the asterisk and parenthesis through, you run the risk of allowing SQL injection passed to your service.” The idea you stated other then a buffer overflow was a SQL injection. Neither of these are valid. You failed to consider XSS and having user involvement at the time. I did not think of this either. If you had suggested this I would have conceded that as an attack vector has I now have. 
>
> The suggestion that an embedded buffer overflow or binary attack against the fax server is still out of the question.
>
> You for example stated:
>
> “The communication is one-way as Craig so eloquently pointed out.  But what if the command is to drop a database?  In that 
> case there was never any intention of receiving data back, it's a malicious vandalism of your database.”
>
> Again, this is not a valid path or attack vector Scott. You are attempting to add too much complexity. So consider a 
> XSS as a simplification of your idea. By over complicating the idea to send SQL commands to an unknown database or 
> worse embed a buffer overflow (which I am still wondering how you could even propose as I see no way to fax a NOP sled) 
> you take the thesis to a level where it may not be supported.
>
> Regards,
>
> Dr Craig Wright
>
>
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