"Leaks such as this threaten ongoing operations, puts at risk the lives of sources, makes it much more difficult to recruit sources, and damages our relationships with our foreign partners," Mueller said. "And consequently, a leak like this is taken exceptionally seriously, and we will investigate thoroughly."
Sen. Chuck Grassley, R-Iowa, pressed Mueller on whether the information had been leaked by the administration for political gain, likening the details on the bomb plot to what he described as the "authorized leaks from the White House about the operation to kill Osama bin Laden." The FBI director declined to answer the question.
The hearing offered an unusually vivid illustration of the Obama administration's hard-line approach to the news media.
The administration took office with a promise of unprecedented transparency, including "“ in a sharp change from the Bush administration -- posting the names of those visiting the White House onto its website. The White House also offered strong support for a so-called shield law preventing reporters working national-security stories from being forced to identify confidential sources.
But those moves have been increasingly outweighed by the administration's aggressive effort to crack down on those responsible for sharing classified information with the news media.
The White House's main tool has been the Espionage Act, a 1917 law passed during the height of World War I as a way of finding and punishing officials passing useful information to enemy countries. The legislation had been used to bring cases against suspected leakers a grand total of three times in the previous 91 years; the Obama administration has invoked it to prosecute six such cases in the past three years alone. If the FBI believes it has found the official or officials who spoke to the AP, that tally will increase to seven.
The first case brought under the Espionage Act targeted Thomas Drake, a whistle blower from the National Security Agency who was indicated for giving a reporter information detailing massive waste, fraud, and inefficiencies at the secretive agency. The Justice Department's case against Drake fell apart days before the trial was set to begin last summer, highlighting the difficulties of winning convictions in such cases.
That hasn't stopped the administration from trying. In January, the Justice Department indicted John Kiriakou, a former CIA officer accused of providing classified information about waterboarding and other controversial interrogation methods to journalists and misleading the agency while trying to get permission to publish a memoir about his time there. The case is ongoing.
The others facing potential prison time for their dealings with the media are former FBI translator Shamai Leibowitz, State Department contractor and analyst Stephen Jin-Woo Kim, former CIA officer Jeffrey Sterling, and Pfc. Bradley Manning, accused of leaking thousands of classified military and State Department documents to online whistle-blower WikiLeaks. Leibowitz was sentenced to 20 months in prison in 2010 for leaking classified information to a blogger regarding Israel's efforts to influence Congress and public opinion; the other cases are continuing.