“Negligence of an employee of an external development company” Nine months after the first leak, Woori Bank’s head office in Jung-gu, Seoul. Yonhap News: An incident occurred in which approximately 17,500 pieces of customer information from Woori Bank were leaked to the outside world. Woori Bank became aware of the leak nine months after the first leak. However, Woori Bank said that an external development company leaked the information due to employee negligence, and because the leaked information is information encrypted with nicknames and linked information (CI), it is impossible to identify customers.