Soufan also described in detail the process of interrogating Abu Zubaydah, which he was involved in. He said that when he and CIA officers used legal techniques, they quickly learned valuable information, including that KSM masterminded the 9/11 attacks. But when a contractor came in and started torturing Zubaydah, he quickly clammed up. Overall, said Soufan, the use of torture was "harmful to our efforts to defeat al-Qaeda."