As with OneCare, Morro will have the same kind of antispyware features that are found in Microsoft's Windows Defender.

Designed to appeal to people who have not bought antivirus software, Morro will use less system resources than OneCare. It will also have fewer features. It will protect PCs from malicious programs such as viruses and Trojans, but will not include the systems management and backup capabilities that come with OneCare.

The free antivirus software will be available in the same markets where OneCare is currently sold, OneCare subscribers will continue to receive support through the end of their subscriptions.

Microsoft shook up the consumer antivirus market when it began selling OneCare in May 2006. Antivirus vendors worried that Microsoft would use its desktop monopoly to push customers to the product, and OneCare itself represented a reinvention of the antivirus category, with its backup and management features and its three-user licensing model.

But the product did not perform well in reviews and ultimately failed to challenge the dominance of antivirus leaders such as Symantec and McAfee.