After months of dormancy a mass mailing email worm has exploded onto the Internet.
Aliz, which affects Windows PCs, was first identified by anti-virus experts back in May but it was only this week that it began spreading rapidly.
MessageLabs, a managed services firm which scans for and blocks viruses in its clients email, recorded only a trickle of incidents of the worm prior to Monday, when it exploded onto the scene. Statistics from MessageLabs record that it blocked Aliz 1849 times yesterday and 769 times so far today, making it the second most common email infector behind the infamous SirCam worm.
Alex Shipp, senior anti-virus technologist at MessageLabs, said that one possible explanation for the spread is that the virus writer placed the code on a Web site but never released it into the wild. According to this theory it's only now that someone emailed it out.
Aliz is spread via the Internet as an infected file attached to an email. The email's subject line is randomly generated from a list of different components but there is an attachment called whatever.exe.
Aliz uses a known exploit, related to the processing of certain unusual MIME types, in certain versions of Outlook Express 5 so as to launch an attachment automatically. The trick, which was also used by the authors of the Nimda worm, means simply previewing an infected email is enough to get infected.
On execution the worm looks in the registry to find a suitable SMTP server address and then sends itself to entries in the Windows Address Book. This is a one-time mailing.
Protection from Aliz has been available from major anti-virus vendors for months and its spread highlights the numerous Windows users who aren't using anti-virus software, and have failed to apply Microsoft's IE patch. ®
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