Newsweek reveals the identity of the previously anonymous source who in 2004 tipped off the New York Times to a secret NSA wiretapping program that was eavesdropping on Americans, and was apparently being concealed from the FISA court which, by law, had to approve such programs.

Thomas Tamm, a veteran prosecutor, learned of the program while working at a Justice Department unit handling wiretaps of suspected terrorists and spies. Here's Newsweek's dramatic description of Tamm's Arlington-parking-garage moment:

For weeks, Tamm couldn't sleep. The idea of lawlessness at the Justice Department angered him. Finally, one day during his lunch hour, Tamm ducked into a subway station near the U.S. District Courthouse on Pennsylvania Avenue. He headed for a pair of adjoining pay phones partially concealed by large, illuminated Metro maps. Tamm had been eyeing the phone booths on his way to work in the morning. Now, as he slipped through the parade of midday subway riders, his heart was pounding, his body trembling. Tamm felt like a spy. After looking around to make sure nobody was watching, he picked up a phone and called The New York Times.

But for Tamm himself, the decision hasn't necessarily worked out well. Reports the magazine:

The FBI has pursued him relentlessly for the past two and a half years. Agents have raided his house, hauled away personal possessions and grilled his wife, a teenage daughter and a grown son. More recently, they've been questioning Tamm's friends and associates about nearly every aspect of his life. Tamm has resisted pressure to plead to a felony for divulging classified information. But he is living under a pall, never sure if or when federal agents might arrest him.

...

Tamm is haunted by the consequences of what he did--and what could yet happen to him. He is no longer employed at Justice and has been struggling to make a living practicing law. He does occasional work for a local public defender's office, handles a few wills and estates--and is more than $30,000 in debt. (To cover legal costs, he recently set up a defense fund.) He says he has suffered from depression.

At the time he made his fateful decision, Tam worked at DOJ's Office of Intelligence Policy and Review (OIPR), which was charged with asking FISA court for permission for national-security wiretaps. But Tamm learned that some wiretap requests bypassed the court and went straight to the Attorney General. These related to what was referred to only as "the program." Though Tamm didn't know it at the time, president Bush had signed a series of secret orders that authorized the NSA for the first time to eavesdrop on phone calls and e-mails between the US and a foreign country without approval by the FISA court.

Here's Newsweek's description of how the program worked:

The NSA identified domestic targets based on leads that were often derived from the seizure of Qaeda computers and cell phones overseas. If, for example, a Qaeda cell phone seized in Pakistan had dialed a phone number in the United States, the NSA would target the U.S. phone number--which would then lead agents to look at other numbers in the United States and abroad called by the targeted phone. Other parts of the program were far more sweeping. The NSA, with the secret cooperation of U.S. telecommunications companies, had begun collecting vast amounts of information about the phone and e-mail records of American citizens. Separately, the NSA was also able to access, for the first time, massive volumes of personal financial records--such as credit-card transactions, wire transfers and bank withdrawals--that were being reported to the Treasury Department by financial institutions. These included millions of "suspicious-activity reports," or SARS, according to two former Treasury officials who declined to be identified talking about sensitive programs. (It was one such report that tipped FBI agents to former New York governor Eliot Spitzer's use of prostitutes.) These records were fed into NSA supercomputers for the purpose of "data mining"--looking for links or patterns that might (or might not) suggest terrorist activity.

Newsweek editors have framed the story as a question: "Is he a hero or a criminal?" reads the sub-hed. But, at least in Tamm's view, we might not have learned about the program had he not made that phone call. Looked at in that light, the answer to Newsweek's question seems clear.