Admitting that failure of linkage of SWIFT to core banking system (CBS) could have led to Rs 11,400 crore fraud at Punjab National Bank, the former head of the scam-hit lender on Friday said there was an urgent need for banks to revisit their surveillance system and plug the loopholes. Usha Ananthasubramanian, who is now managing director and CEO of Allahabad Bank, said at her bank also SWFIT is not linked to CBS, and the process of linking both the systems is currently on.