"A particularly malicious worm (a self-replicating computer virus) is currently trying to spread itself through many of the world's largest instant messaging and social networks, including Windows Live Messenger 2009. We’re very serious about protecting our customers, and are pursuing multiple avenues to help stop its progress. The worm spreads by inserting a link into an IM conversation with a person whose computer is already infected. When someone clicks the link, it opens in a browser, downloads the worm on the recipient’s computer, and then repeats this process.Continue reading : Security alert: Active links in Messenger 2009 temporarily turned off to prevent a malicious worm
Normally, when Messenger sees a web address in a conversation it is turned into a hyperlink which, when clicked, automatically opens in a web browser. This feature makes it very easy for the malicious worm to be unknowingly installed on your computer by clicking on the link and being sent to a web site containing the malicious software. We’re pursuing a number of activities to help protect you, working actively with industry experts and law enforcement to help stop this criminal activity.
Most notably, we’ve temporarily turned off active hyperlinks for web addresses sent in IM conversations using Windows Live Messenger 2009. You will still be able to copy a web address and paste it into a browser window if you know it to be safe, but by removing active hyperlinks from Messenger 2009, we’re taking a significant step towards stopping the unintentional spreading of this worm..."
Posted @ Inside Windows Live