New submitter alexander_686 points out a Bloomberg article about the cause of Knight Capital Group's $440 million algorithmic trading disaster from a couple weeks ago. The report says a dormant software system was accidentally activated on August 1, which immediately began increasing stock trade volumes by a factor of 1,000. The Wall Street Journal has further details: "Knight Capital Group Inc.'s accidental trades earlier this month were triggered by a flawed upgrade of trading software that caused an older trading system connected to the computer code to inadvertently go 'live' on the market, according to people familiar with the matter. The errors at Knight on Aug. 1 involved new code the Jersey City, N.J.-based brokerage designed to take advantage of the launch of a New York Stock Exchange trading program, which was introduced that day to attract more retail-trading business to the Big Board, the people say. ... When NYSE Euronext trading floor officials called Knight at about 9:35 a.m. to try to pinpoint the cause of unusual swings in dozens of stocks, just after the Big Board opened for trading, Knight traders and their supervisors had a difficult time detecting where in its systems the problem was located, say people familiar with the morning's events. The NYSE had to call Knight several times before deciding to shut the firm off, the people say."