"If you think of basic security flaws as low-hanging fruit, then we've taken away all of the watermelons lying on the ground," Cushman said. "I've never seen any other company invest this much to prevent attacks against their software," said Dan Kaminsky, one of 20 security consultants hired by Microsoft to help tighten up Vista. "As soon as I walked in the door, I was handed a full guide documenting all of the threat models for each feature."

Kaminsky completed his work on the Vista project last month.

Kaminsky said he believes that Vista is now on par or better than operating systems such as Linux and Apple Computer Inc.'s Mac OS X.