Another new version of the MyDoom worm is spreading, and like last week's variant it uses Yahoo! as part of its infection routine.

MyDoom-Q is similar to earlier MyDoom variants. It normally spreads via email, with a spoofed sending address and a variety of different subject lines. The body of an infected email contains random sentences, some of which refer to the attached Zip file that contains viral code. Once opened, this payload file copies itself to the Windows system directory as "winlibs.exe." The executable contains a list of dozens of common first and surnames that it puts through Yahoo's 'People Search' function in an attempt to find more email addresses to target for infection. It also scours files on the infected user's hard drive for future potential victim.

MyDoom-M (AKA MyDoom-O), released last week, also tried to exploit search engines in a similar way. The earlier version of the email worm plugged domain names into Yahoo, Google, AltaVista and Lycos search engines in an effort to find valid email addresses. This caused slowdowns and prevented many people from being able to search the web using Google, the worst affected site. However, Yahoo's People Search function appears to be responding normally despite the arrival on the scene of MyDoom-Q last night.

According to early analysis, MyDoom-Q does NOT leave a backdoor on infected PCs. This marks it out from previous MyDoom variants which used this feature to create a network of compromised, zombie PCs.

MyDoom-Q is far less virulent than its more aggressive predecessor, with most AV firms putting it into the medium-risk category. As usual My-Doom-Q is a Windows-only menace. Standard precautions apply avoid opening unsolicited attachments, even when they appear to come from people you trust, and update AV tools to detect the worm. AV vendors are in the process of updating signature definitions to recognise MyDoom-Q with protection largely in place.

Even AV firms are getting sick of the sight of fresh versions of MyDoom with both Sophos and F-Secure appealing to members of the computer underground to turn in MyDoom';s author. In January, Microsoft put up a $250,000 bounty for information leading to the arrest and conviction of MyDoom’s creator. SCO has also put up a $250,000 bounty on head of the same, elusive individual. ®

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