A new internet worm that steals information from users' computers and attempts to shut down two websites is spreading, according to antivirus vendors.

The worm, dubbed Mimail.C, is a variant of the W32.Mimail worm that surfaced in August. Antivirus software vendors including Symanteq, F-Secure and Network Associates rate the worm a medium-level threat.

Mimail.C was discovered Friday, the vendors said in bulletins on their websites. It arrives as an email with 'our private photos' in the subject line and an attached Zip archive file called 'photos.zip'. The sender's address is faked as 'james' at the receiver's domain and the body of the message promises revealing photos of a girl at a beach, the antivirus vendors said.

The worm with its attachment was mass-mailed; this most likely started its propagation, according to an alert from Network Associates.

Infection starts when the recipient unpacks the photos.jpg.exe file from the attachment and runs it. The worm will harvest email addresses from the user's PC to mail itself to. It will also send information captured from applications the user has open to certain email addresses programmed into the malicious code.

The worm will also attempt to launch a denial of service (DoS) attack on websites at darkprofits.com and darkprofits.net, the vendors said.

All of the main antivirus vendors said they have updated their software to protect customers against the newly discovered worm.