REDMOND, Wash. (AP) - Microsoft Corp. plans to release a test version of its free computer security program Tuesday.

Microsoft Security Essentials is designed to find and kill malicious software that steals passwords and other personal information or turns PCs into spam distribution hubs.

Once the program is installed, Microsoft says the software will update itself automatically. It will keep a low profile unless dangerous software is detected.

Security Essentials will compete with rival subscription programs from McAfee Inc. and Symantec Corp., and with several other free packages.

A final version is expected in the fall. After it launches, Microsoft will discontinue its $50 security system, called Windows Live OneCare.