Security chief says US surveillance has foiled terror plots

America’s sweeping surveillance programmes have foiled 50 terrorist plots, including one directed at the New York Stock Exchange, according to the director of the National Security Agency.

General Keith Alexander said the two recently disclosed operations one that gathers US phone records and another that is designed to track the use of US-based internet servers by foreigners with possible links to terrorism are critical in the terrorism fight.

Intelligence officials last week disclosed some details on two thwarted attacks one targeting the New York subway system, one to bomb a Danish newspaper office that had published the cartoon depictions of the Prophet Mohammed.

General Alexander and Sean Joyce, deputy director of the FBI, offered additional details on two other foiled plots, including one targeting Wall Street.