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Re: Backdoor not recognized by Kaspersky
From: Cael Abal <lists2 () onryou com>
Date: Wed, 03 Mar 2004 09:56:34 -0500

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 password 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 new 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.

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

Cael

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