Penetration Testing mailing list archives
RE: FAX virus
From: "THORNTON Simon" <Simon.THORNTON () swift com>
Date: Wed, 21 Nov 2007 12:56:38 +0100
Hi, I'm not sure that you can say categorically that it is out of the question to fax a virus. From a conventional fax machine or a scanner I would agree but via the use of raw fax files I'm not so sure. I seem to remember, maybe incorrectly, that a G3 Fax (CCITT T.4) transmission uses a modified form of TIFF file for each page image it sends. The page header is sent during the 300 baud handshake phase that precedes each page. If the target system had software with a vulnerability in the receiving software then it might be theoretically possible to compromise that system. I haven't verified this but you could produce the base component of this as follows: convert MYPIC.gif MYPIC.pbm pbm2g3 MYPIC.pbm >MYPIC.g3 Where: MYPIC.gif is any source document/image you want to use You would then modify MYPIC.g3 to contain a buffer overflow or similar and then send it using fax s/w (sendfax?) that supports raw g3 file sending. Inserting data into the page header sequence might also be an avenue of research. I don't imagine it working on a standard fax machine but fax software running on a PC?. Just a thought.... :-) Simon -----Original Message----- From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of cwright () bdosyd com au Sent: Sunday, November 18, 2007 08:55 To: pen-test () securityfocus com Subject: Re: FAX virus I have though about this for a while following some of the earlier posts. Faxing a virus is out of the question and I have not seen anything to state the contrary. I have thought of an alternate path to loading a virus bases on a network OCR'd fax server. In the scenario, we have to assume that the system is sending the output to a web front end or HTTP enabled email (not that uncommon). There are a few assumptions that I will place first. - The system has no input filters and prints all characters to the email, web app. - The OCR engine is highly accurate and does not add spaces etc. - The email or web app displays exactly what it received Now given that scenario, we have a possible XSS (cross-site-scripting) attack. If there are no filters for an outgoing connection (i.e. no firewall/proxy that strips scripts) and the client browser/email application allows access to the Internet, the attacker could create a script in the page that makes a call to an external system to download a file. In a simple scenario, an AV server on the proxy level should get this. However, a script could also embed a simple XOR obfuscation key to modify the downloaded code. On the web server it would be inert. When XOR'd with the key in the script (after being downloaded and installed), this will thus bypass the AV server (if there is one) and install the malware on the users system. So the faxing of the virus is still out of the equation, but it does allow an infection (or other attack) vector. Regards, Dr Craig Wright (GSE-Compliance) ------------------------------------------------------------------------ This list is sponsored by: Cenzic Need to secure your web apps NOW? Cenzic finds more, "real" vulnerabilities fast. Click to try it, buy it or download a solution FREE today! http://www.cenzic.com/downloads ------------------------------------------------------------------------
Current thread:
- Re: FAX virus cwright (Nov 18)
- RE: FAX virus Ramsdell, Scott (Nov 19)
- Re: FAX virus M.B.Jr. (Nov 24)
- Re: FAX virus Steve Friedl (Nov 27)
- RE: FAX virus THORNTON Simon (Nov 24)
- Re: FAX virus M.B.Jr. (Nov 26)
- <Possible follow-ups>
- Re: RE: FAX virus cwright (Nov 19)
- Re: FAX virus Alcides (Nov 24)
- RE: FAX virus Ramsdell, Scott (Nov 19)