As a result, they are exposed to various kinds of operational risk. For a bank active in derivatives trading, a breakdown in computer systems for even a relatively short time could be disastrous - preventing it from monitoring its changing market positions and disrupting its capacity to trade and to settle outstanding transactions.
I recently heard a keen observer predict that the next big banking disaster would come from a (hypothetical) major international bank losing track of its derivatives positions for 24 hours. To protect against such events, banks invest heavily in the integrity of their computer systems, as well as in back-up and disaster recovery facilities.