full-disclosure - Re: Multiple AV Vendor IncorrectCRC32BypassVulnerability.

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From: steve_scholz at sybari.com (Steve Scholz)
Subject: Re: Multiple AV Vendor
	IncorrectCRC32BypassVulnerability.

Sat Mar 12 10:26:35 2005 (4320-4292), "INFORMATION: Internet scan found
virus:

   Folder: SMTP Messages\Internal

   Message: test b

   File: Antigen_b.zip

   Incident: Large uncompressed size

   State: Removed"

The Antigen_s.zip does not contain a valid Eicar this info when repaired
and opened is X5O!P%@AP[4\PZX

We did catch it with a file filter.

Sat Mar 12 10:32:29 2005 (4320-4292), "INFORMATION: Internet scan found
virus:

   Folder: SMTP Messages\Internal

   Message: Fw: test

   File: Antigen_s.zip->eicar.com

   Incident: FILE FILTER=  *.com

   State: Removed"

What was your intent with these files?

Steve Scholz
Corporate Sales Engineer-North America
Sybari Software, Inc.
631-630-8556 Direct
516-903-2464 Mobile

Email:  Steve_scholz@...ari.com

MSN IM:Steve_Scholz@....com (email never checked) 

-----Original Message-----
From: full-disclosure-bounces@...ts.grok.org.uk
[mailto:full-disclosure-bounces@...ts.grok.org.uk] On Behalf Of bipin
gautam
Sent: Saturday, March 12, 2005 2:58 AM
To: Steve Scholz; vuln@...unia.com
Cc: full-disclosure@...ts.grok.org.uk; vuldb@...urityfocus.com
Subject: RE: [Full-disclosure] Re: Multiple AV Vendor
IncorrectCRC32BypassVulnerability.

> While it might be a vulnerability if the file is
> extracted which it hasto be to be executed the 
> desktop scanner will detect it at that time. 
> Multiple layers of defense is your best option 
> As far as number 3 Antigen detects Eicar.

YAP, i never reported Antigen vulnerable to the 3'rd
one.

Though, In Local file header if you modify "general
purpose bit flag" 7th & 8'th byte of a zip archive
with \x2f Antigen is also seem to be vulnerable! While
most unzip utilities are transperently able to extract
SUCH* archive without any problem! Though,currently my
only source of verifying this is via
www.virustotal.com and some others. [Go, TRY IT
THEER!]
http://www.geocities.com/visitbipin/gpbf.zip

> I can see if there is anything
> else that you do not
> think Antigen is doing correctly.

 (O;

For instant,
In the 'local file header" & "data descriptor" if you
change the  compressed size and uncompressed size to
ZERO[iDEFENSE] or greater than the actual file size or
less than the actual file size still there are many AV
that can't scan the file properly. 
http://www.geocities.com/visitbipin/Antigen_b.zip
http://www.geocities.com/visitbipin/Antigen_s.zip

Moreover there are unzip utilities that goes to a loop
if the filesize is changed to ffffffff ! Lets hope, AV
don't have such faulty code!

Just run the file through www.virustotal.com and
you'll see. (I know, they aren't using up-to-date scan
engine)

Thanks,
bipin

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