Appearing before the House Appropriations Committee to discuss his department's budget, Holder said they were investigating high-frequency trading to see whether it violated insider trading laws.
"The department is committed to ensuring the integrity of our financial markets," said Holder. "We are determined to follow this investigation wherever the facts and the law may lead."
A lot of interest has been generated about high-frequency trading after author Michael Lewis appeared on CBS' 60 Minutes and called the U.S. stock markets "rigged" and said that high-frequency trading was robbing millions of their money.
High-speed computers and servers hooked up to the stock markets give high-frequency traders precious milliseconds to place their orders before ordinary investors, and thereby make risk-free profits, he said.
The Federal Bureau of Investigation has also said they are looking into high-frequency trading and whether it violates insider trading laws.
New York Attorney General Eric Schneiderman, the Commodity Futures Trading Commission and the Securities and Exchange Commission have all launched independent investigations into the practice.
When questioned by Rep. Jose Serrano, D-N.Y., about whether such practices violate the law, Holder responded, "I am really getting up to speed on this," to which Mr. Serrano replied, "we all are."
Holder said that what concerns federal investigators is whether such trading practices are giving traders "an appropriate advantage, an information advantage... Milliseconds can matter, so we're looking at this to try to determine if any federal criminal laws have been broken."
[Wall Street Journal]