The software is primarily meant to combat low adoption rates as a whole and especially in poorer countries, where many residents can't afford the often subscription-based suites from other firms or aren't aware of free options. These unguarded PCs often pose the greatest risk by serving as infection points for more serious viruses, Endpoint chief Roger Kay tells Microsoft.

Microsoft says the software will be optional and ship for Windows XP, Vista and 7 systems sometime during the second half of 2009. OneCare is being phased out for retail on June 30th as a result of the move, though the company hasn't said if or when it plans to phase out the service through other channels.

The introduction of "Morro" is potentially critical for Microsoft, whose platform has been the target of more attacks and which necessitated a major turnaround in security policy during the Windows XP era and has been the subject of criticism from rivals less subject to these attacks, including Apple. However, the company's move also raises concerns of unfair competition as it will provide much of the same functionality as pay-only apps from McAfee and Norton as well as partly or entirely free options such as AVG.