Penetration Testing mailing list archives
RE: FAX virus
From: "Ramsdell, Scott" <Scott.Ramsdell () cellnethunt com>
Date: Mon, 19 Nov 2007 13:46:51 -0500
Craig, I find your statement suggesting you "have thought of an alternate path to loading a virus" to be disingenuous. The following is my reply to you on 03.05.07 regarding a question posed by the security basics list member Alcides, who was asking if his OCR software process running on a Windows box, which happened to process faxes, was a concern. "From what Alcides says, he has a fax server (this will convert from analog to digital, BTW) and he has a process running on a Windows box that accepts input from the fax server. I merely cautioned him about properly sanitizing the input from the fax server to the Windows service! Very valid concern." This was my original reply to Alcides "Others on this list, and especially on the Pen Test list, can speak much more suitably than I can on this issue, but I will contribute the following. This depends entirely on how the input to the "document processing system" is sanitized. If the document processing system blindly accepts user input as valid, then you potentially have an issue. If the document processing system runs as a service on your Windows boxes, check to ensure that it launches with an account that does not have System or Admin rights on the box." So, eight months ago, the security basics mailing list discussed this (before it boiled over to the pentest list), while you initiated a tirade concerning the impracticality of faxing a virus (which was not at all the point). I question your motivation for discussing your "thought" eight months after I and others suggested the existence of a concern in not sanitizing OCR input to a Windows service, and for releasing your "thought" on a completely different list than the one Alcides originally posted on. Kind Regards, Scott Ramsdell CISSP CCNA MSCE -----Original Message----- From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of cwright () bdosyd com au Sent: Sunday, November 18, 2007 1:55 AM 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 ------------------------------------------------------------------------ ------------------------------------------------------------------------ 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)