Last month Sen. Richard Shelby of Alabama, ranking Republican on the Senate Select Committee on Intelligence, set about investigating an apparent congressional leak. It involved a National Security Agency intercept of a telephone conversation in Arabic conducted on Sept. 10, 2001, and proclaiming that the following day was to be "zero hour."Unable to find the source of the leak themselves, the chairmen of the House and Senate intelligence committees, Rep. Porter J. Goss (R-Fla.) and Sen. Bob Graham (D-Fla.), asked the FBI for assistance, pledging the full cooperation of committee members and their staffs. And that is what the FBI...