SAN FRANCISCO: An Internet worm, disguised as a screensaver cartoon of former US President Bill Clinton playing the saxophone, that can delete files and slow network connections was spreading on Friday, antivirus software vendors said.

The worm, dubbed "MyLife.b," was rated a medium risk because of its demonstrated ability to lure users to open it and the way it tries to delete files, said April Goostree, virus research manager at McAfee.com Corp. It affects Microsoft Outlook users. However, the Outlook E-mail Security Update, downloadable for Office 2000 and 98 users and included in Outlook 2002, blocks executable attachments, Microsoft said.

The worm is embedded in an executable file in the attachment that comes with an e-mail with the subject line "bill caricature." The e-mail also attempts to mislead people into thinking it has been scanned by an antivirus vendor and found to be safe. In the body of the e-mail is the message "No Viruse Found" (sic) and "McAfee.com." However, Goostree said anti-virus messages are never delivered to customers that way.

Once the attachment is opened, the worm drops a copy of itself in the computers' system folder and if the computer is rebooted between the hours of 8 am and 9 am it will try to delete all files on the C, D, E and F drives and certain files in the Windows system directory, according to Goostree.

The worm also may slow down computer users' e-mail and Internet connections, according to McAfee.com. Goostree said she did not know where the worm originated, but noted that Australia has been hit particularly hard. The worm appeared to have started slowing down by midday on Friday, she said.

British-based e-mail security services provider MessageLabs Inc. said MyLife was the most active virus on Friday, with nearly 2,000 samples intercepted. It has affected users in 29 countries, most strongly in Great Britain, the United States and Australia, the company's Web site said.