According to the reports, the bank’s system didn’t properly record withdrawals made around midnight — effectively spitting out cash without removing the total from a user’s account. Normally, that might send up a red flag that a transaction had failed, but Qisheng allegedly inserted scripts into the system that suppressed those alerts.
Qisheng started pulling out money in November 2016, but it wasn’t until January 2018, some 1,358 withdrawals later, that the bank discovered the bad code in its system and brought him to the authorities.
Read More.. Source The Verge