Microsoft has announced they will be releasing their own antivirus software very soon. Given the codename, "Morro," the new software will be a competitor to the major antivirus software makers like Symantec and McAfee.
The main goal of this software is to remove trojans, spyware and viruses. That's it. It's currently undergoing testing and is likely to see a beta very soon for the public. What's interesting, is this antivirus software will be free for Windows users, which is likely to stick a thorn in the side of its competitors.
Microsoft tried the antivirus market before with their OneCare bundle, though it required an annual fee. It never really took hold, so now the free price tag is likely to bring in added interest.