Just after I post my incredibly brief summary of computer security I get this... Microsoft will be releasing security software that helps prevent "spyware". I didn't bother to discover if it might include virus protection or "adware" protection or any other kind of "malware" and I won't until it's released. Too much software has a reputation for claiming features it will have and then don't.
My boss has a good read on these feature claims:
More Information about the Microsoft Security Software
CNN.com - Microsoft may charge extra for security software - Dec 16, 2004