Bagle author learns his lesson from anti-spam

Three new Bagle variants discovered over the weekend differ from previous incarnations because they use an anti-spam trick to try and avoid detection by antivirus software, but experts believe that the attempt won't succeed. The Bagle worm installs a back door on infected systems and could allow the machine to be used as an email gateway for sending spam. Since the beginning of March, Bagle has arrived under the guise of an encrypted Zip file with a password included in the email text.

Within days, antivirus companies updated their products to look for the password and decrypt the Zip file, but the Bagle author has now released these three new versions of the worm that produce the password in the form of a graphic or picture file, so a simple text scan of the infected email would not find the password. This trick is commonly used by websites when displaying email addresses to hide from web-bots that trawl the internet looking for potential spam targets.

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