Speaking to a congressional committee Tuesday morning, General Keith Alexander revealed that government surveillance efforts have thwarted “over 50” possible terrorist threats since 9/11, including plans to bomb the New York Stock Exchange and NYC subway system. Alexander, who heads the NSA, specifically noted that programs like the Verizon metadata collection may have been able to stop 9/11 if they had been in place at the time. He suggested that this program as well as “other intelligence” — which he did not disclose — assisted in foiling the 50 or so threats. Alexander noted that the foiled plots occurred worldwide, not just domestically, although further details for most incidents aren’t being publicly given at the moment. According to NBC News, a congressional committee will be briefed on classified details of all of the attacks this Wednesday.