Vendors Warn of New Sober Worm Variants

Yet more variants of the mass-mail Sober worm are making the rounds ofthe Net and could infect Windows-based computers, antivirus firmswarned Tuesday. Thus far, the variants present a low risk and haven’tbeen widely distributed.

Both Kaspersky Lab and Symantec Corp. have detected worm variants.Kaspersky noted three variants of E-mail-Worm.Win32.Sober, whichSymantec identified as W32.Sober.S@mm.

The variants are modifications of the same program, said Kaspersky,which is based in Moscow. A “large number of samples” of the variantshave been intercepted in e-mail traffic, indicating that the worms arespreading by spam containing infected messages, Kaspersky said in astatement. The variants arrive as an attachment to infected messages.

The messages might not have a subject line or text, but can beidentified by the attachment name. The attachment names thus faridentified are: Exceltab-packed_list.exe; Liste.zip;Reg-List-Dat_Packer2.exe; reg_text.zip; Word-Text.zip;Word-Text_packedList.exe; Word-Text_packedList.zip.

The worm activates only if a computer user clicks on the attachment,which causes a false error message, “WinZip Self-Extractor.WinZip_Data_Module is missing ~Error,” to pop up, Kaspersky said. Theworm variants copy themselves to the Windows system directory and thenregisters the files to the system registry so that the worm launchesevery time Windows is rebooted.

The worm uses its own SMTP (Simple Mail Transfer Protocol) engine tospread, Symantec said. Spam that it generates is in either English orGerman, said Symantec, which is based in Cupertino, California. Massmailing of spam containing the worm could clog mail servers or degradenetwork performance, the company said. Instructions for removing theworm from infected systems can be found at Symantec’s Web site,http://www.symantec.com, by clicking on the Sober variant listing under”latest threats.”

As always, the antivirus companies advise that computer users exercise caution in opening attachments.

By Nancy Weil – IDG News Service (Boston Bureau)