WASHINGTON, Jan. 16 – 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, which was collecting much of the data by eavesdropping on some Americans’ international communications and conducting computer searches of foreign-related phone and Internet traffic, that the unfiltered information was swamping investigators. Some F.B.I. officials and prosecutors also thought the checks, which sometimes involved interviews by agents, were pointless intrusions on Americans’ privacy.
“We’d chase a number, find it’s a school teacher with no indication they’ve ever been involved in international terrorism – case closed,” said one former FBI 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.”
F.B.I. field agents, who were not told of the domestic surveillance programs, complained 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 Al Qaeda operative.” He said, “I would always wonder, what does ‘suspected’ mean?”