Hi Andreas Marx,
It is ironic that now the AV programs implemented the "smart" file format
checking, but "forgot" about file extensions :)
I think, that "smart" file format checking must be complemented with the
"smart" file extension checking.
Regards,
Andrey Bayora.
----- Original Message -----
From: "Andreas Marx" <gega-it@web.de>
To: "Andrey Bayora" <andrey@securityelf.org>; <bugtraq@securityfocus.com>
Sent: Wednesday, October 26, 2005 12:50 PM
Subject: Re: Multiple Vendor Anti-Virus Software Detection Evasion
Vulnerability through
Hi!
Thanks, that's interesting to read. In 2000, I've found and suggested the
following in an article I've written for the Virus Bulletin magazine
<http://www.virusbtn.com> :
"[...] Some scanners do not actually scan all files even when set to "scan
all files" or when the mask "*.*" is used. Most of the time at least some
infected .BAT, .VBS and .COM files will be missed if they have non-standard
extensions. This happens when the scanner checks the file extension, not the
content, in order to scan solely for this kind of virus. It would be a good
idea for vendors to make a "smart" scan to find out the (hopefully) correct
file format. If there is more than one possibility (like ASCII text or a
.COM file), all possible supported formats should be scanned. [...]"
You can find this (Title: "The Usual Suspects ? Part 1", Dec 2000) and
more related articles here:
<http://www.av-test.org/sites/references_papers.php3?lang=en>
cheers,
Andreas Marx
CEO, AV-Test.org
<http://www.av-test.org>
Multiple Vendor Anti-Virus Software Detection Evasion Vulnerability
through
forged magic byte.
AUTHOR: Andrey Bayora (www.securityelf.org)
For more details, screenshots and examples please read my article "The
Magic
of magic byte" at www.securityelf.org . In addition, you will find a
sample
"triple headed" program which has 3 different 'execution entry points',
depending on the extension of the file (exe, html or eml) - just change
the
extension and the SAME file will be executed by (at least) THREE
DIFFERENT
programs! (thanks to contributing author Wayne Langlois from
www.diamondcs.com.au).
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