U.S. officials are starting to crack down on high-frequency trading, a practice that uses computers to buy and sell stocks in microseconds. The opening salvo is an indirect crack at the increasingly controversial Wall Street practice, and it comes from New York Attorney General Eric Schneiderman, who filed a civil suit Wednesday against British banking behemoth Barclays PLC for allegedly lying about favoring high-frequency trading in its stock trading business.

The suit alleges that Barclays lied about "dark pool" trading venues -- stock trading arenas where buy and sell orders aren't publicly reported -- by telling clients they were designed to protect them from high-frequency trading firms but actually constructing the dark pool to favor such lightning-fast trading.

Schneiderman called Barclays operations "a systematic pattern of fraud and deceit" that favored high-frequency trading, rather than human investors seeking protection from the controversial computer-enabled practice, according to The Guardian. On top of that, Barclays allegedly downplayed the presence of high-frequency trading in the dark pool venue and falsely portrayed how client orders were fulfilled.

"The facts alleged in our complaint show that Barclays demonstrated a disturbing disregard for its investors in a systematic pattern of fraud and deceit," Schneiderman said. "Barclays grew its dark pool by telling investors they were diving into safe waters. According to the lawsuit, Barclays' dark pool was full of predators -- there at Barclays' invitation."

Schneiderman is increasingly investigating high-frequency trading, which some experts say now accounts for the majority of stock market trades, following the March release of a tell-all book about the high-tech financial device by Michael Lewis: "Flash Boys: A Wall Street Revolt." In the book, Lewis argues that high-frequency trading has essentially rigged the stock market, in a pattern of abuse that has cost investors an estimated $5 billion per year at minimum.

High-frequency trading uses sophisticated computer algorithms to trade securities in tiny short-term microtrades that take milliseconds or microseconds. High-frequency traders often make only a fraction of a cent in each trade, but make up for low margins by upping the volume of trades, which can number in the millions. The practice has existed since at least 1999 -- the U.S. Securities and Exchange Commission authorized electronic exchanges the year before -- but with the growth of computing power and intense research into trading algorithms, something of a high-frequency trading "arms race" has been occurring in recent years: The faster the high-frequency trading firms can get in and out of a transaction, the more volume and profits they can make.

European countries have proposed banning or restricting high-frequency trading, and U.S. officials, especially Schneiderman, have been influenced by Lewis' recent book to begin looking into the practice. Besides being an allegedly unfair market practice, according to Lewis, high-frequency trading and other algorithmically triggered market actions are widely believed to have at least contributed to the May 6 Flash Crash in 2010, sometimes called "The Crash of 2:45," in reference to the fact that the Dow Jones lost nearly 10 percent of its value, and then recovered, within minutes of 2:45 p.m. According to the SEC report on the Flash Crash, for example, high frequency traders accounted for nearly half of the trading volume in the 14 seconds between 2:45:13 and 2:45:27, adding to the market's volatility until some electronic trading systems were put on hold.