A Finnish security firm has warned MSN Messenger users that the latest beta of the IM client might not be what it seems. F-Secure said that a variation of the Virkel instant messaging virus has been circulating amongst MSN users, posing as a leaked beta version of MSN Messenger 8.

The virus uses the 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 unauthorised software on the machine. Victims are being infected by clicking and installing the BETA8WEBINSTALL.EXE file that is being distributed via these download links, F-Secure said.

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

Microsoft has, in fact, released a beta version of its next-generation instant messaging client to a select number of users, but the software is not called MSN Messenger 8, according to a spokeswoman for the company. The beta software of the product, called Windows Live Messenger, was released on 12 December, she said.

"The anti-virus community is currently tracking a malicious threat which poses as "MSN Messenger 8 Working BETA" and may spread to users via MSN Messenger," Microsoft's spokeswoman said. "We highly discourage anyone from downloading any betas from any site other than Microsoft/MSN sanctioned sites as we are not able to guarantee the authenticity of the files."