Microsoft uncovered more than 1,800 bugs in Office 2010 by tapping into the unused computing horsepower of idling PCs, by running millions of "fuzzing" tests, said Tom Gallagher of Microsoft. “Fuzzing is a practice employed by software developers & security researchers, searches for flaws by inserting data into file format parsers to see where programs fail by crashing. Because some crash bugs can be further exploited to successfully hack software, allowing an attacker to insert malicious code, fuzzing’s of great interest to both legitimate and criminal researchers looking for security vulnerabilities. Client software installed on systems throughout Microsoft's network automatically kicks in when PCs are idle, such as on weekends, to run fuzzing tests "We would do millions of [fuzzing] iterations each weekend," Gallagher said -- up to 12 million in some cases.” Gallagher declined to quantify number of flaws found via fuzzing that qualified as vulnerabilities, saying only that Office 2010 team did uncover security bugs in process and patched them during development. Some of those vulnerabilities've already been addressed in older editions of Office, Gallagher added, because information obtained by fuzzing Office 2010 code was checked against code in earlier versions -- such as Office 2007 and Office 2003 -- then patched during Office 2010's development. Non-security bugs discovered in Office 2010 that also exist in previous editions will be fixed in those versions' upcoming service packs, Gallagher said.