The new worm is called Winevar and was first spotted in South Korea. Its release was possibly intended to coincide with the Anti-Virus Asia Researchers (AVAR) conference, which was held in Seoul last week, according to security company F-Secure.
E-mail messages containing the worm may contain the subject "Re: AVAR (Association of Anti-Virus Asia Researchers)," according to F-Secure.
The worm is also known as W32/Winevar.A, W32/Korvar, W32/Winevar@mm, I-Worm.Winevar and the "Korean Worm".
According to advisories, the worm appears to be a variant of the recent Bridex or "Braid" worm. But whereas Bridex simply gathered information on the systems it infected, Winevar can cause real damage to machines.
Once infected machines are rebooted, the worm displays a dialogue titled "Make a fool of oneself" with the message "What a foolish thing you have done!" Clicking on an OK button on the dialogue deletes all files on the computer's hard drive that are not currently opened, according to the security advisories.
Like Bridex, Winevar takes advantage of the known IFRAME vulnerability in Microsoft's Internet Explorer Web browser and Microsoft mail clients such as Outlook and Outlook Express. That vulnerability allows attachments in HTML-format e-mail messages to be opened without user interaction.
Also like Bridex, Winevar deposits a variant of the Funlove virus on infected machines once it is run and attempts to shut down processes used by antivirus software. According to Kaspersky Labs, there are signs that the worm may also be programmed to conduct a denial of service attack against antivirus software maker Symantec's Web site.
Winevar spreads itself by searching out e-mail files and extracting addresses from them. The worm then uses Simple Mail Transport Protocol (SMTP) to e-mail copies of itself to those addresses, using random series of numbers to disguise the name of the attachment containing the worm, further complicating the task of identifying infected e-mail messages.
Most leading antivirus companies have posted updated definitions for the new worm and instructions on removing the worm from infected machines. Users who suspect they are infected are advised not to restart their machine before removing the worm's files.