Microsoft Security Update instant message alerts notify you when time sensitive information about Microsoft products has been posted on the Security Web site. You can choose to receive these alerts through MSN Messenger or Windows Messenger, your e-mail, or a mobile device like your cell phone or PDA. Register at the Microsoft Security Alerts Web page.

Information on Microsoft Security Update Instant Message Alerts as well as RSS Feeds for Security Bulletins, the Microsoft Security Notification Service, and the Microsoft Security Notification Service Comprehensive Edition can be found at this location:

http://www.microsoft.com/technet/security/bulletin/notify.mspx

SIDEBAR: Oh, and it looks like they are using LiveMessage, which is what powers my .NET IM alerts for this weblog:

• Check out LiveMessage from MessageCast
•  Get alerts for this weblog