No area of the banking system is immune from fraudsters - not even the security team designed to prevent them.
For the successful fraudster, the rewards can be enormous and the risks small. Even if caught the chances of being publicly punished are remote. Some have even received work devising security systems for those they have sought to defraud.
The most vulnerable institutions are those going through an internal upheaval, so particularly susceptible at present are those with incompatible computer systems involved in Big Bang marriages. Also at risk are rapidly expanding organisations or those switching to different types of business - such as the transition from commercial to investment banking.
The most common, and often most lucrative, type of bank fraud is diversion of money transfers. The computer password to the money transfer system is the modern equivalent to the combination to the bank vaults. Yet, because people still don't think of it that way, it is often easy to find out. It is also much less conspicuous to use than its predecessor. Most security systems are based on two people with different passwords to authorise every transaction. To keep the two apart, banks rely on the physical separation of departments.