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Re: Backdoor not recognized by Kaspersky
From: Bart.Lansing () kohls com
Date: Wed, 3 Mar 2004 09:58:20 -0600

Cael...take a more sensible approach...no password parsing to scan
needed...have the AV/mail gateways stop any zip with any executable inside.
You don't need to use the password to see that there is an
.exe/.scr/.com/.whatever inside a zip.  You see it, you nuke the zip. If
your policies allow zipped executables to meander through your mail system
as long as they pass a virues scan, you must have damned busy 0 days.  This
ain't complicated...at all.

Bart Lansing
Manager, Desktop Services
Kohl's IT

Leave passworded .zips alone -- take the sensible approach and catch an
infected file once it's been extracted.


full-disclosure-admin () lists netsys com wrote on 03/03/2004 08:56:34 AM:

Another variant against the Netsky virus. It's is packed with
UPX. It spreads with the password protected zip file, which
gets bypassed through all most all the AV scanners with
latest signature updates because No AV can decrypt it
without the password. (though password is in the message
content), we humans tend to open it after reading the message.

Kaspersky, NAI and possibly some other AV-vendors now parse the
from the body of the email to extract the zip and then scan it.
Obviously this only helps if it can scan the complete email i.e. on the

mailserver. They might need to adapt to new varitions of how the
password is included in the body, which will take some analysis when
variants emerge.

Does anyone else find this new development a bad idea?

I'm of the mindset that anti-virus companies should stick with what
they're good at -- namely, detecting and handling infected files.  It
seems a bad idea to start down the natural language processing road.
Are they scanning just for Bagle/Beagle style e-mail, or are their
methods more general?  What about messages of the form:

'Password is a long yellow fruit enjoyed by monkeys.'

What about messages in languages other than English?  I can easily see
this becoming an arms-race, and one the anti-virus folks have no chance
of winning.

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