Sunday evening saw reports of yet another email-borne worm affecting MS Windows. Bagle spreads via email, following the opening of an attachment. Sound familiar?

Bagle comes as a standard email from a random mail address with 15kb attachment, the subject line of which is imaginatively titled 'Test'. The creative energy continues undiluted in the body of the message with the unsigned phrase 'Test, yep'. Should anyone be silly enough to open the randomly-named attachment, Bagle copies itself to the system directory under the name 'bbeagle.exe', and registers the following file in the registry:

Once lodged in the registry, bagle runs "calc.exe", before attempting to download and execute "TrojanProxy.Win32.Mitgleider" from a variety of remote websites. The worm has a built-in expiry date of January 28.

Finally, Bagle scans the infected hard drive searching for email addresses, before sending itself on using its own SMTP engine. AV firm Kaspersky Labs defines Bagle as a moderate threat.The sensible response to yet another email worm is the update your AV signatures, and avoid opening email unsolicited attachments. ®