If you use MSN Messenger and receive an IM with a link to a leaked "MSN Messenger 8 Beta" from a friend in your list: don't open it!
Security firm F-Secure is warning about this new worm that spreads from a fake website, where the author pretends to have a copy of MSN Messenger 8 beta.
The download BETA8WEBINSTALL.EXE from that fake site actually installs a worm that will by turn send instant messages to everyone on the user's MSN list with links to download their "beta". The malware also connects to a bot network.
Although there is a MSN Messenger 8 Beta around (I am running it now) you can only get into the beta if you receive an invitation via email, and possibly your friend will tell you beforehand when sending it.