In a recent financial fraud case, city employees in Brooklyn, New York, accessed electronic databases to defraud the city of $20 million. Several employees in collusion with the former deputy tax collector completely erased or reduced $13 million in property taxes and $7 million in accrued interest that taxpayers owed. In exchange for this service, the taxpayers paid the employees involved bribes of 10 to 30 percent of their bills.

Required
Discuss the control techniques that could prevent or detect this fraud.