The FBI acknowledged Wednesday it improperly accessed Americans' telephone records, credit reports and Internet traffic in 2006, the fourth straight year of privacy abuses resulting from investigations aimed at tracking terrorists and spies.

Testifying at a Senate Judiciary Committee hearing, Mueller raised the issue of the FBI's controversial use of so-called national security letters in reference to an upcoming report on the topic by the Justice Department's inspector general.

An audit by the inspector general last year found the FBI demanded personal records without official authorization or otherwise collected more data than allowed in dozens of cases between 2003 and 2005. Additionally, last year's audit found that the FBI had underreported to Congress how many national security letters were requested by more than 4,600.

In contrast to the strong concerns expressed by Congress and civil liberties groups after last year's inspector general's report was issued, Mueller's disclosure drew no criticism from senators during just over two hours of testimony Wednesday.
Following last year's audit, the Justice Department enacted guidelines that sternly reminded FBI agents to carefully follow the rules governing national security letters.

"The credibility factor shows there needs to be outside oversight," said former FBI agent Michael German, now a national security adviser for the American Civil Liberties Union. "There were guidelines before, and there were laws before, and the FBI violated those laws," German said. "And the idea that new guidelines would make a difference, I think cuts against rationality."