Beginning with a report written for the 15-nation European Parliament last year, public concern has been building in many countries around Echelon, the code name for a worldwide surveillance network run by the NSA and its partners in Britain, Australia, Canada and New Zealand.
The paranoia may have peaked on Oct. 21, known on the Internet as "Jam Echelon Day," when organizers urged e-mail users around the world to send as many messages as possible containing words such as "bomb" and "assassinate" in an attempt to overload NSA supercomputers that sort through millions of intercepted communications looking for threats to national security.
Yet serious questions remain. Does the NSA listen in on U.S. citizens, either on purpose or by accident? Does it trade information with other countries? What does it do when it comes across commercial secrets or evidence of high-level corruption?
"Right now Echelon is a black box, and we really don't know what is inside it," said Barry S. Steinhardt, associate director of the American Civil Liberties Union. "It is more than reasonable, given the past excesses of the NSA, that it may be being misused."
Even basic facts about Echelon are so hard to verify that the ACLU this month put up a Web site, www.echelonwatch.org, to serve as a repository of information about the global spy network, whose existence the NSA has never publicly acknowledged.
Civil libertarians first became alarmed about Echelon in January 1998 after the European Parliament's report claimed that "within Europe, all e-mail, telephone and fax communications are routinely intercepted by the United States National Security Agency."
The report unleashed a roiling controversy throughout Europe that continues to this day. Beyond obvious privacy concerns, officials across the continent wondered whether the NSA was stealing trade secrets from European companies and handing them to American competitors, a charge U.S. officials strenuously deny.
Congress, meanwhile, has added a provision to the fiscal 2000 intelligence budget that requires the NSA to report within 60 days on its legal standards for intercepting communications in the United States and abroad. House and Senate conferees approved the language Nov. 5.
"Echelon gives every appearance of a program that is far broader than it ought to be and poses serious questions about constitutionality," said Rep. Robert L. Barr Jr. (R-Ga.), who sponsored the reporting requirement.
Barr, a former CIA analyst, said no one in Congress has asked the NSA hard questions about electronic surveillance since 1975, when a committee headed by then-Sen. Frank Church (D-Idaho) revealed that the government had improperly intercepted Americans' telegrams for 30 years and had unlawfully eavesdropped on domestic dissidents in the 1960s.
"What we have here is an operation that has been ongoing for many years that nobody really seems to have a handle on," said Barr, adding that the House Government Reform Committee, of which he is a member, plans to hold hearings on Echelon early next year.
Although the NSA is Maryland's largest employer, with well over 30,000 employees, it keeps a very low profile. It was only in recent years that the agency even put up signs along the Baltimore-Washington Parkway to its headquarters at Fort Meade, which reportedly has five acres of supercomputers underground.
Without confirming or denying Echelon's existence, senior U.S. officials familiar with the NSA's operations deny that the agency violates the civil rights of U.S. citizens. They say the NSA strictly adheres to the 1978 Foreign Intelligence Surveillance Act (FISA), which resulted from the Church committee's revelations.
FISA prohibits the NSA from deliberately eavesdropping on Americans either in the United States or overseas, unless the agency can establish probable cause to believe that they are agents of a foreign government committing espionage or other crimes.
When any communication to, from or about an American is incidentally intercepted by the NSA in the course of intelligence gathering abroad, the law says, such information cannot be disseminated within the government and must be destroyed within 24 hours unless it contains "a threat of death or serious bodily harm" to some person.
Unlike foreign operations, all domestic NSA surveillance requires prior court approval. But even in such cases, the law calls for "minimization procedures" -- such as deleting the names of third parties -- to limit the infringement on privacy.
Defense officials also deny that the NSA and its foreign partners evade prohibitions on domestic spying by trading information with each other.
"I can say categorically that NSA is as careful as any civil libertarian would want it to be in adhering to the rules," said Stewart A. Baker, the NSA's former general counsel, now a private communications lawyer in Washington. "There is an ingrained discipline about that, right down to the lowest levels of the agency."
Indeed, the NSA's troubles in Congress began this spring when Rep. Porter J. Goss (R-Fla.), chairman of the House Permanent Select Committee on Intelligence, asked the agency for internal documents about its compliance with FISA because he thought NSA lawyers were too cautious in approving new surveillance programs.
When the agency declined his request on grounds of attorney-client privilege, Goss erupted, saying the committee had never been stonewalled in such fashion. Barr immediately joined the dispute from the opposite flank, suggesting that the NSA had refused Goss's request because it was violating Americans' privacy by indiscriminately vacuuming up communications.
Barr's concerns were echoed in Europe by a second, even more detailed report on electronic surveillance, this time for the European Union. Not only the United States, but dozens of countries now have the ability to intercept "every modern type of high capacity communications" including pager messages, cellular phone calls and Internet e-mail, wrote the author, British journalist and physicist Duncan Campbell.
Campbell claimed that "major governments are routinely utilising communications intelligence to provide commercial advantage to companies and trade." But he also noted in the report that the NSA and other spy agencies are struggling to deal with the spread of encryption, fiber optic cables and other new technologies.
Contrary to the claims made on Jam Echelon Day, U.S. defense officials said, the NSA has neither the computer power nor the huge number of linguists and analysts necessary to snatch every e-mail, fax and telephone conversation around the world.
"This argument that NSA is out there sucking in all your e-mails into its basement and reading everything -- that's just crazy," said one official.
Steven Aftergood, director of a research project on government secrecy at the independent Federation of American Scientists, said the controversy is a case study of the public's willingness to believe almost anything about the NSA, and the NSA's unwillingness to explain what it's really doing.
"The Echelon story satisfies some widespread need to believe in a government that's out of control," Aftergood said. "But underneath all of this is an important policy issue, and that is, when enough American citizens become concerned about an intelligence policy issue, they are entitled to get an answer -- and so far they haven't gotten one."