MSN Messenger users who may think they're getting a sneak peak at the latest version of Microsoft's instant messaging client are in for a nasty surprise, a Finnish security firm is warning.

A variation of the Virkel instant messaging virus has been circulating amongst MSN users, posing as a leaked beta version of MSN Messenger 8, according to F-Secure.

The virus uses the MSN Messenger client to send download links to all of an infected user's contacts, and connects the user's machine to a second "botnet" server, which could then could be used to install unauthorized software on the machine.

Infection SpreadsVictims are being infected by clicking and installing the BETA8WEBINSTALL.EXE file that is being distributed via these download links, F-Secure says.

"There is no MSN Messenger 8 yet. Not in public beta anyway." writes F-Secure Chief Research Officer Mikko Hypponen, writing on a company blog.

Microsoft recently released MSN Messenger 7.5.

A representative of Microsoft's public relations agency was not able to comment for this story.