Patch releases push down Microsoft's stock, researcher says

Microsoft's stock price regularly takes a hit on the days it issues security patches, according to research released Monday. The company's stock price typically rebounds the next day, after investors realize that the slight decline on Patch Tuesday -- as Microsoft's regularly scheduled update release is known -- was unwarranted, said McAfee.

But the fluctuations are so small that it would be tough for all but the best-funded investor to take advantage of the price movement, said Dave Marcus, McAfee's director of research. "Are the swings huge? Not really. But patches do have a trackable effect," Marcus said.

McAfee researcher Anthony Bettini, who authored a paper the company published yesterday, said that there was a correlation between Microsoft share-price fluctuations and the patch cycle. According to data Bettini tallied from 2006 and 2007, as well as thus far in 2008, there is a downward trend in the price of Microsoft's stock on the average Patch Tuesday.