“The program was codenamed SHAMROCK and known to only a few people within the government. Every day, a courier went up to New York on the train and returned to Fort Meade with large reels of magnetic tape, which were copies of the international telegrams sent from New York the preceding day using the facilities of three telegraph companies. The tapes would then be electronically processed for items of foreign intelligence interest, typically telegrams sent by foreign establishments in the United States or telegrams that appeared to be encrypted. Telegrams sent by US citizens to foreign destinations were also present in the tapes NSA received.”
