Microsoft has lost another key employee to Amazon.com. George Stathakopoulos, a computer security expert who'd been with Microsoft for nearly two decades, took a job at Amazon, Microsoft spokesman Lou Gellos confirmed. Stathakopoulos was general manager of the Trustworthy Computing Group at Microsoft and was front and center in Microsoft's efforts to combat the Conficker worm last year.

Stathakopoulos is part of a growing list of Microsoft veterans who have jumped to Amazon, including, most recently, longtime Windows vice president Mike Nash. Others who have made the leap include Brian Valentine, now senior VP of Amazon’s e-commerce platform; data center guru James Hamilton; and computer security expert Steve Riley. The poaching is part of an evolving rivalry between the two Seattle area tech giants, which are increasingly competing in areas like cloud computing.

Stathakopoulos once worked under Nash and was involved in various aspects of Microsoft's security strategy. It was not immediately clear what role he's taking with Amazon. Amazon spokeswoman Mary Osako didn't immediately respond to a request for comment.

Computerworld reports Stathakopolous will be replaced at Microsoft by Matt Thomlinson, "formerly senior director of security engineering with the Trustworthy Computing group."

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