A variant of the Sober mass-mailing worm appears to be gaining more traction as leading security vendors increase their threat levels.
Increasing prevalence of the W32/Sober.C worm prompted Network Associates Inc. on Sunday to raise its risk assessment to medium from low. Sober.C is most active in Germany, where e-mail security vendor MessageLabs Inc. said 83 percent of samples had originated.
Other security vendors all have rated Sober.Cs threat as low or medium. F-Secure Corp. tagged it a medium threat, ranking it a level 2 threat out of three. Symantec Corp. rated it as a level 2 threat out of five, or a low threat. MessageLabs also consider the risk “low,” while saying that it has intercepted a “significant number of copies” of the worm.
Sober.C first appeared on Saturday, and New York-based MessageLabs reported its highest number of interceptions of the worm on Sunday.
Sober.C, once activated, e-mails itself to a users Microsoft Outlook address book and sends outgoing messages through its own SMTP engine, said Network Associates, of Santa Clara, Calif. Along with e-mail, Sober.C can spread through peer-to-peer filing sharing networks.
The infected messages can appear in either English or German and use a variety of subject lines and file attachment names. The attachments end in one of the following extensions: com, bat, cmd, pif, scr or exe.
The executed worm displays a fake error message that begins with the attached file name in quotes.
Sober.C, written in Visual Basic, can infect systems running Windows 2000, Windows 95, Windows 98, Windows NT and Windows Server 2003.
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