Last November, Microsoft announced that it would be phasing out its Windows Live OneCare subscription security service, effectively replacing it with a free antivirus and antispyware program. That program, Microsoft Security Essentials, debuted today as a public beta for users in the U.S., Israel, China and Brazil. It works on Windows XP, Windows Vista and the Windows 7 beta and release candidate.

Security software vendors will no doubt be watching closely to see how the program is received. Microsoft says Security Essentials, previously known by the code-name Morro, will be offered as a standalone download, separate from Windows 7. However, Microsoft's presence in the industry and position in the market still give it plenty of ways to make sure consumers know about the new offering.

Symantec, for one, is taking it serously to offer some pointed commentary on the subject. "Morro is essentially a stripped-down version of Microsoft's failed OneCare product," said senior product management director David Cole in an email to InternetNews.com earlier this month. "It didn't offer adequate protection when it was payware, and it offers even less as freeware."

The Windows Live OneCare team has defended the quality of the product in the past.

For more details, Windows author and ZDNet blogger Ed Bott posted a preliminary review of Microsoft Security Essentials last week, coming away with a favorable initial impression.

"You can bet that the beta release will be seriously tested by independent labs and especially by Microsoft’s for-profit competitors in the coming weeks. If it has any weaknesses, expect to see them heavily publicized," Bott wrote. "Meanwhile, I’m sufficiently impressed by MSE in operation to give it a more in-depth workout on multiple systems here."

Microsoft says its current plan is to cap downloads of the Microsoft Security Essentials beta at 75,000, although it may adjust that number to allow more depending on demand.