It is absolutely impossible, that somebody in a position like Jerome Kerviel can hold trading positions for 50 bn Euros and burn 10% of that amount. It is impossible, because
- banks nowadays would never rely on simple password protection for their trading systems.
- they all have state-of-the-art identity management in place and manage business roles in a way that one single trader could not crash the whole bank
- such big deals would always be routed through acknowledgement processes where duties are segregated
- Strong Authentication techniques and strict authorization would let all employees of a bank feel, that it is impossible to operate with multiple identities falsifying acqunowledgement processes
- risk dashboards would turn red and start screaming long before such a damage occurs