Last year, fewer than 300 phone numbers were checked against the database of millions of US phone records gathered daily by the NSA in one of the programs, the intelligence officials said in arguing that the programs are far less sweeping than their detractors allege.
No other new details about the plots or the countries involved were part of the newly declassified information released to Congress yesterday and made public by the Senate Intelligence Committee.
The release of information follows a bruising week for US intelligence officials who testified in Congress, defending programs that were unknown to the public and some lawmakers until they were revealed by a series of media stories in The Guardian and The Washington Post newspapers, leaked by former NSA contractor Edward Snowden, who remains in hiding in Hong Kong.
Intelligence officials said yesterday that both NSA programs are reviewed every 90 days by the secret court authorised by the Foreign Intelligence Surveillance Act. Under the program, the records, showing things like time and length of call, can only be examined for suspected connections to terrorism, they said.
The officials offered more detail on how the phone records program helped the NSA stop a 2009 al-Qaeda plot to blow up New York City subways. They say the program helped them track a co-conspirator of al-Qaeda operative Najibullah Zazi though it's not clear why the FBI needed the NSA to investigate Zazi's phone records because the FBI would have had the authority to gather records of Zazi's phone calls after identifying him as a suspect, rather than relying on the sweeping collection program.