UPDATE 3-Microsoft will soon unveil free anti-virus software

"Microsoft's free product is basically a stripped down version of the OneCare product Microsoft pulled from the shelves," said Symantec Consumer division president Janice Chaffin. "A full Internet security suite is what consumers require today to stay fully protected."

Joris Evers, a spokesman for No. 2 security software maker McAfee, said his company is already enjoying strong growth despite competition from free anti-virus products that are on the market.

"On a level playing field, we are confident in our ability to compete with anyone who might enter the marketplace," he said.

A spokeswoman for Trend Micro Inc (4704.T), the No. 3 player, declined to comment. (Reporting by Jim Finkle; Editing by Steve Orlofsky, Brian Moss, Richard Chang)