When the National Security Agency trains its agents in the highly technical art of eavesdropping, they naturally need to practice.
And the law gives them the right to practice on you.
NSA agents can hone their listening skills and test their equipment on the most intimate telephone calls of ordinary U.S. citizens, as long as notes and tapes are destroyed "as soon as reasonably possible."
"We listened to all the calls in and out of Washington," says one former NSA linguist, recalling a class at the Warrenton Training Center, a CIA communications school on a Virginia hilltop. "We'd listen to senators, representatives, government agencies, housewives talking to their lovers."
As the students prepared for overseas assignments in the mid-1980s class, the linguist recalls, they tuned their receivers to a nearby AT&T microwave tower, scanning for calls and punching in phone numbers.
Is NSA Big Brother? Absolutely not, its officials say. In public appearances, NSA Director John M. "Mike" McConnell declares flatly that the agency "does not spy on Americans."
But as the little-known legal loophole for training intelligence agents suggests, the story of NSA and the privacy of Americans is not quite so simple.
True, NSA's mission is to spy on foreigners. And employees attest to a law-abiding culture in recent years that strongly discourages illegal excursions into domestic eavesdropping.
But in its first two decades, NSA routinely scanned every telegram entering or leaving this country and targeted the communications of anti-Vietnam War and civil rights activists, accumulating files on 75,000 Americans.
After a 1975 congressional inquiry, the agency was placed under new restrictions by executive orders and the Foreign Intelligence Surveillance Act (FISA) of 1978. But it is not just paranoid outsiders who remain uneasy about a secret eavesdropping agency in an open society.
"It always worried me. What if that is used on American citizens?" wonders former Sen. Dennis DeConcini, an Arizona Democrat and chairman of the intelligence committee until early this year. "It is chilling. Are they listening to my private conversations on my telephone?"
THEY MAY BE LISTENING -- legally. Laws protecting U.S. citizens from NSA eavesdropping are not as airtight as many Americans may suppose:
NSA is permitted to intercept any communication as long as one end is in a foreign country, and its global electronic net inevitably captures Americans' phone calls, faxes and computer messages. The law prohibits only the deliberate targeting of Americans and restricts the release to other agencies of the names of Americans picked up.
Eavesdropping on U.S. soil by NSA is overseen by a highly unusual, top-secret court that is virtually invisible to the public despite its remarkable record: In 16 years, it has never refused an NSA or FBI request for an eavesdropping warrant.
The rules that tell NSA eavesdroppers how to handle Americans' communications - contained in a volume called U.S. Signals Intelligence Directive 18 - are classified top secret and cannot be viewed by the citizens they are written to protect.
The few lawsuits filed against NSA by Americans who believe the agency has invaded their privacy have gone nowhere, because courts have accepted NSA's argument that its work is so secret that merely allowing a lawsuit to proceed would endanger national security.
Without ever "spying on Americans," NSA routinely infringes on their privacy.
"Even when they target foreigners, they end up picking up a lot of Americans," says Mark H. Lynch, an attorney who tracked NSA for the American Civil Liberties Union from 1977 to 1985.
Just ask former Maryland Rep. Michael D. Barnes. His calls to Nicaraguan government officials were intercepted and recorded by NSA - as he learned only after transcripts were leaked by the Reagan White House, he says.
"Reporters told me right-wingers were circulating excerpts from phone conversations I'd had," says Mr. Barnes, now a Washington lawyer. He says the calls included one to the Nicaraguan foreign minister protesting his government's declaration of martial law.
On another occasion, Mr. Barnes says, the director of central intelligence, William J. Casey, showed him a Nicaraguan Embassy cable intercepted by NSA that reported a meeting between embassy officials and a Barnes aide. Mr. Casey told him he should fire the aide; Mr. Barnes angrily replied that it was perfectly proper for his staff to meet with foreign diplomats.
Mr. Barnes says he did not object to being overheard. But he said the incidents were a reminder of the potential for the abuse of NSA's awesome eavesdropping capacity.
"I was aware that NSA monitored international calls, that it was a standard part of intelligence gathering," he says. "But to use it for domestic political purposes is absolutely outrageous and probably illegal."