Virus writers in malicious code hide-and-seek

Bagle Zip shenanigans test new AV techniques

A fresh angle of attack by virus writers is challenging new anti-virus techniques.

The latest versions of the Bagle worm spreading this week contain a malicious payload hidden in a password-protected zip archive. This is the first time the trick has been used to spread the virus in the wild, though the ruse has been seen in lab copies of viral code (e.g. Fearso), dating from last Summer.

The password-protected Zip archive technique enables virus writers to hide malware in files which gateway AV scanners normally can't open, so skipping one layer of protection commonly used by many large companies.

Conventional desktop AV scanners would still block infection at the point a user unzips password-protected viral files - assuming the correct signature update is available - but it's obviously desirable to stop malicious code reaching the user's PC in the first place.

AV firms including Kaspersky Labs and Bucharest-based BitDefender this week introduced upgrades to thwart the password-protected virus ploy.

Kaspersky Anti-Virus, for example, can now detect protected Zip archives, scan the email body for the password and then unpack and check the attachment for viruses. The new protection is been delivered alongside new AV signature downloads from the Russian vendor.

Gateway security appliance vendor Network Box has taken a similar approach. Other vendors can be expected to follow suit.

All of which will make IT systems as secure as they were against virus infestation before the new malware technique burrowed its way into public consciousness -i.e. not very secure at all. ®

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