Price isn't right for new Bagle variant

Worm du jour

Yet another variant of the mass-mailing Bagle worm began spreading widely yesterday.

Bagle-AQ (AKA Bagle-AL or Bagle-AC) normally spreads by emails containing an infectious attachment. The attachment name is variable, but always contains the word "price". The attachment is always ZIP, although it could sometimes be encrypted. In these cases the email contains the password in an image.

This archive contains a HTML file and the worm's payload, an EXE file. When the HTML file is accessed, the worm uses a well-known (Object Data) vulnerability in Internet Explorer to load and execute its payload. Once this payload is executed, infected PCs begin spamming out copies of the worm to email addresses harvested from the hard disks of compromised machines.

Bagle-AQ can also spread over P2P networks. Files infected with the worm but posing as useful utilities or games are copies into P2P share directories of compromised machines.

Like previous variants of Bagle, the worm contains a backdoor which allows the author of the virus to control infected machines. Bagle-AQ also tries to terminate various AV programs on infected machines.

Bagle-AQ spread rapidly initially, possibly because of the use of spamming software by its unknown authors. As usual, Bagle-AQ is a Windows-only menace.

Standard defensive precautions apply: avoid opening unsolicited attachments, even when they appear to come from people you trust; update AV tools to detect the worm; update IE with Microsoft's latest patches. ®

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