The loss of 4.9 bln is exorbitant. It's almost all of the bank's profits in one year. This trader worked on a share portfolio. That means, more or less, he was in charge of buying shares and then selling them on when they've increased in price. But every trader has an investment limit. This is set by the risk management control department, who work directly under general management. It's usually fixed on the experience of the particular trader. It's like in a casino, where they fix the bids so as not to ‘break the bank'. But no trader, not even the seniors, would be able to take risks with the amount we're talking about. It's impossible. Every order is registered by a master IT system which sets off an alert if fixed amounts are passed. Therefore, this trader must have found a way around the risk-management system. For example by using some his colleagues' accounts to buy or sell shares, or by recording false transactions to balance his account. This trader must have worked for a long time in middle-office and therefore the service that registers all orders. That's rare. In general traders start working in the front office from the beginning, and they don't have inside knowledge of the very complex order-placing system. This person might therefore know the weaknesses of the system. But it's very difficult to understand how he managed such an exorbitant fraud."