Microsoft Readies Free PC Security Software

In fact, it's important that Microsoft's competitors stay in business, Burch said.

"If there was only one solution out there addressing threats, all the malicious software developers out there would have a very easy target," she said.

The security software will come as a free download, but it won't be part of Microsoft's Windows 7 operating system, which goes on sale in October. Bundling the two could be fodder for antitrust complaints.

After the final version launches, Microsoft will discontinue its existing security program, the more robust $50 Windows Live OneCare.

In a statement Thursday, antivirus software maker Symantec objected to Microsoft's description of Security Essentials.

"Referring to Microsoft's basic antivirus and antispyware product as an essential security solution is misleading," said Dave Cole, a senior director at Symantec. He said PC users need the extra firewall protection, spam fighters and other features that come with subscription security programs.

"The freeware space is crowded and Microsoft is just joining the fray," Cole said.