WASHINGTON, May 23 (Xinhua) -- The U.S. National Security Agency (NSA), armed with details of billions of telephone calls, used phone records linked to the Sept. 11, 2001, attacks to create a template of how phone activity among terrorists looks, the USA Today newspaper reported Tuesday.

    The template, current and former intelligence officials were quoted as saying, was created from a secret database of phone call records collected by the spy agency.

    The template has been used since Sept. 11 to identify calling patterns that indicate possible terrorist activity, and among the patterns examined were flurries of calls to U.S. numbers placed immediately after the domestic caller received a call from Pakistan or Afghanistan.

    The call records, which include information on calls made before the Sept. 11 attacks, are the electronic information that is logged automatically each time a call is initiated.

    In addition to the number from which a call is made, the detail records are packed with information, such as the number called; the route a call took to reach its final destination; the time, date and place where a call started and ended; and the duration ofthe call. The records also note whether the call was placed from a cellphone or from a traditional "land line."

    Using computer programs, the NSA searches through the database looking for suspicious calling patterns, the report quoted the officials as saying.

    Calls coming into the country from Pakistan, Afghanistan or the Middle East, for example, are flagged by NSA computers if they are followed by a flood of calls from the number that received the call to other U.S. numbers.

    The spy agency then checks the numbers against databases of phone numbers linked to terrorism, the officials said.

    It is not clear how much terrorist activity, if any, the data collection has helped to find, the report said. Enditem