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)
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