WASHINGTON - In the anxious months after the Sept. 11 attacks, the National Security Agency began sending a steady stream of telephone numbers, e-mail addresses and names to the F.B.I. in search of terrorists. The stream soon became a flood, requiring hundreds of agents to check out thousands of tips a month.
But virtually all of them, current and former officials say, led to dead ends or innocent Americans.
F.B.I. officials repeatedly complained to the spy agency that the unfiltered information was swamping investigators. The spy agency was collecting much of the data by eavesdropping on some Americans' international communications and conducting computer searches of phone and Internet traffic. Some F.B.I. officials and prosecutors also thought the checks, which sometimes involved interviews by agents, were pointless intrusions on Americans' privacy.
Yassin Aref (Chip East/Reuters)
As the bureau was running down those leads, its director, Robert S. Mueller III, raised concerns about the legal rationale for a program of eavesdropping without warrants, one government official said. Mr. Mueller asked senior administration officials about "whether the program had a proper legal foundation," but deferred to Justice Department legal opinions, the official said.
President Bush has characterized the eavesdropping program as a "vital tool" against terrorism; Vice President Dick Cheney has said it has saved "thousands of lives."
But the results of the program look very different to some officials charged with tracking terrorism in the United States. More than a dozen current and former law enforcement and counterterrorism officials, including some in the small circle who knew of the secret program and how it played out at the F.B.I., said the torrent of tips led them to few potential terrorists inside the country they did not know of from other sources and diverted agents from counterterrorism work they viewed as more productive.
"We'd chase a number, find it's a schoolteacher with no indication they've ever been involved in international terrorism - case closed," said one former F.B.I. official, who was aware of the program and the data it generated for the bureau. "After you get a thousand numbers and not one is turning up anything, you get some frustration."
Intelligence officials disagree with any characterization of the program's results as modest, said Judith A. Emmel, a spokeswoman for the office of the director of national intelligence. Ms. Emmel cited a statement at a briefing last month by Gen. Michael V. Hayden, the country's second-ranking intelligence official and the director of the N.S.A. when the program was started.
"I can say unequivocally that we have gotten information through this program that would not otherwise have been available," General Hayden said. The White House and the F.B.I. declined to comment on the program or its results.
The differing views of the value of the N.S.A.'s foray into intelligence-gathering in the United States may reflect both bureaucratic rivalry and a culture clash. The N.S.A., an intelligence agency, routinely collects huge amounts of data from across the globe that may yield only tiny nuggets of useful information; the F.B.I., while charged with fighting terrorism, retains the traditions of a law enforcement agency more focused on solving crimes.
"It isn't at all surprising to me that people not accustomed to doing this would say, 'Boy, this is an awful lot of work to get a tiny bit of information,' " said Adm. Bobby R. Inman, a former N.S.A. director. "But the rejoinder to that is, Have you got anything better?"
Several of the law enforcement officials acknowledged that they might not know of arrests or intelligence activities overseas that grew out of the domestic spying program. And because the program was a closely guarded secret, its role in specific cases may have been disguised or hidden even from key investigators.
Still, the comments on the N.S.A. program from the law enforcement and counterterrorism officials, many of them high level, are the first indication that the program was viewed with skepticism by key figures at the Federal Bureau of Investigation, the agency responsible for disrupting plots and investigating terrorism on American soil.
All the officials spoke on condition of anonymity because the program is classified. It is coming under scrutiny next month in hearings on Capitol Hill, which were planned after members of Congress raised questions about the legality of the eavesdropping. The program was disclosed in December by The New York Times.
The law enforcement and counterterrorism officials said the program had uncovered no active Qaeda networks inside the United States planning attacks. "There were no imminent plots - not inside the United States," the former F.B.I. official said.
Some of the officials said the eavesdropping program might have helped uncover people with ties to Al Qaeda in Albany; Portland, Ore.; and Minneapolis. Some of the activities involved recruitment, training or fund-raising.
But, along with several British counterterrorism officials, some of the officials questioned assertions by the Bush administration that the program was the key to uncovering a plot to detonate fertilizer bombs in London in 2004. The F.B.I. and other law enforcement officials also expressed doubts about the importance of the program's role in another case named by administration officials as a success in the fight against terrorism, an aborted scheme to topple the Brooklyn Bridge with a blow torch.
Some officials said that in both cases, they had already learned of the plans through interrogation of prisoners or other means.
Immediately after the Sept. 11 attacks, the Bush administration pressed the nation's intelligence agencies and the F.B.I. to move urgently to thwart any more plots. The N.S.A., whose mission is to spy overseas, began monitoring the international e-mail messages and phone calls of people inside the United States who were linked, even indirectly, to suspected Qaeda figures.
Under a presidential order, the agency conducted the domestic eavesdropping without seeking the warrants ordinarily required from the secret Foreign Intelligence Surveillance Court, which handles national security matters. The administration has defended the legality of the program, pointing to what it says is the president's inherent constitutional power to defend the country and to legislation passed by Congress after the Sept. 11 attacks.
Administration officials told Mr. Mueller, the F.B.I. director, of the eavesdropping program, and his agency was enlisted to run down leads from it, several current and former officials said.
While he and some bureau officials discussed the fact that the program bypassed the intelligence surveillance court, Mr. Mueller expressed no concerns about that to them, those officials said. But another government official said Mr. Mueller had questioned the administration about the legal authority for the program.
Officials who were briefed on the N.S.A. program said the agency collected much of the data passed on to the F.B.I. as tips by tracing phone numbers in the United States called by suspects overseas, and then by following the domestic numbers to other numbers called. In other cases, lists of phone numbers appeared to result from the agency's computerized scanning of communications coming into and going out of the country for names and keywords that might be of interest. The deliberate blurring of the source of the tips caused some frustration among those who had to follow up.
F.B.I. field agents, who were not told of the domestic surveillance programs, complained that they often were given no information about why names or numbers had come under suspicion. A former senior prosecutor who was familiar with the eavesdropping programs said intelligence officials turning over the tips "would always say that we had information whose source we can't share, but it indicates that this person has been communicating with a suspected Qaeda operative." He said, "I would always wonder, what does 'suspected' mean?"
"The information was so thin," he said, "and the connections were so remote, that they never led to anything, and I never heard any follow-up."
In response to the F.B.I. complaints, the N.S.A. eventually began ranking its tips on a three-point scale, with 3 being the highest priority and 1 the lowest, the officials said. Some tips were considered so hot that they were carried by hand to top F.B.I. officials. But in bureau field offices, the N.S.A. material continued to be viewed as unproductive, prompting agents to joke that a new bunch of tips meant more "calls to Pizza Hut," one official, who supervised field agents, said.
The views of some bureau officials about the value of the N.S.A.'s domestic surveillance offers a revealing glimpse of the difficulties law enforcement and intelligence agencies have had cooperating since Sept. 11.
The N.S.A., criticized by the national Sept. 11 commission for its "avoidance of anything domestic" before the attacks, moved aggressively into the domestic realm after them. But the legal debate over its warrantless eavesdropping has embroiled the agency in just the kind of controversy its secretive managers abhor. The F.B.I., meanwhile, has struggled over the last four years to expand its traditional mission of criminal investigation to meet the larger menace of terrorism.
Admiral Inman, the former N.S.A. director and deputy director of C.I.A., said the F.B.I. complaints about thousands of dead-end leads revealed a chasm between very different disciplines. Signals intelligence, the technical term for N.S.A.'s communications intercepts, rarely produces "the complete information you're going to get from a document or a witness" in a traditional F.B.I. investigation, he said.
Some F.B.I. officials said they were uncomfortable with the expanded domestic role played by the N.S.A. and other intelligence agencies, saying most intelligence officers lacked the training needed to safeguard Americans' privacy and civil rights. They said some protections had to be waived temporarily in the months after Sept. 11 to detect a feared second wave of attacks, but they questioned whether emergency procedures like the eavesdropping should become permanent.
That discomfort may explain why some F.B.I. officials may seek to minimize the benefits of the N.S.A. program or distance themselves from the agency. "This wasn't our program," an F.B.I. official said. "It's not our mess, and we're not going to clean it up."
The N.S.A.'s legal authority for collecting the information it passed to the F.B.I. is uncertain. The Foreign Intelligence Surveillance Act requires a warrant for the use of so-called pen register equipment that records American phone numbers, even if the contents of the calls are not intercepted. But officials with knowledge of the program said no warrants were sought to collect the numbers, and it is unclear whether the secret executive order signed by Mr. President Bush in 2002 to authorize eavesdropping without warrants also covered the collection of phone numbers and e-mail addresses.
Aside from the director, F.B.I. officials did not question the legal status of the tips, assuming that N.S.A. lawyers had approved. They were more concerned about the quality and quantity of the material, which produced "mountains of paperwork" often more like raw data than conventional investigative leads.
"It affected the F.B.I. in the sense that they had to devote so many resources to tracking every single one of these leads, and, in my experience, they were all dry leads," the former senior prosecutor said. "A trained investigator never would have devoted the resources to take those leads to the next level, but after 9/11, you had to."
By the administration's account, the N.S.A. eavesdropping helped lead investigators to Iyman Faris, an Ohio truck driver and friend of Khalid Shaikh Mohammed, who is believed to be the mastermind of the Sept. 11 attacks. Mr. Faris spoke of toppling the Brooklyn Bridge by taking a torch to its suspension cables, but concluded that it would not work. He is now serving a 20-year sentence in a federal prison.
But as in the London fertilizer bomb case, some officials with direct knowledge of the Faris case dispute that the N.S.A. information played a significant role.
By contrast, different officials agree that the N.S.A.'s domestic operations played a role in the arrest of an imam and another man in Albany in August 2004 as part of an F.B.I. counterterrorism sting investigation. The men, Yassin Aref, 35, and Mohammed Hossain, 49, are awaiting trial on charges that they attempted to engineer the sale of missile launchers to an F.B.I. undercover informant.
In addition, government officials said the N.S.A. eavesdropping program might have assisted in the investigations of people with suspected Qaeda ties in Portland and Minneapolis. In the Minneapolis case, charges of supporting terrorism were filed in 2004 against Mohammed Abdullah Warsame, a Canadian citizen. Six people in the Portland case were convicted of crimes that included money laundering and conspiracy to wage war against the United States.
Even senior administration officials with access to classified operations suggest that drawing a clear link between a particular source and the unmasking of a potential terrorist is not always possible.
When Michael Chertoff, the homeland security secretary, was asked last week on "The Charlie Rose Show" whether the N.S.A. wiretapping program was important in deterring terrorism, he said, "I don't know that it's ever possible to attribute one strand of intelligence from a particular program."
But Mr. Chertoff added, "I can tell you in general the process of doing whatever you can do technologically to find out what is being said by a known terrorist to other people, and who that person is communicating with, that is without a doubt one of the critical tools we've used time and again."
William K. Rashbaum contributed reporting from New York for this article.
Copyright 2006The New York Times Company