单项选择题

In many business, computers have largely replaced paperwork, because they are fast, flexible, and do not make mistakes. As one banker said, "unlike humans, computers never have a bad day." And they are honest. Many banks advertise that their transactions(业务，事务)are "untouched by human hands" and therefore safe from human temptation. Obviously, computers have no reason to steal money. But they also have no conscience(良心) ,and the growing number of computer crimes shows they can be used to steal.
Computer criminals don’t use guns, and even if they are caught, it is hard to punish them because there are not witness and often no evidence. A computer can not remember who used it. It simply does what it is told. The head teller(银行的出纳员)at a New York City bank used a computer to steal more than one and a half billion dollars in just four years. No one noticed this theft because he moved the money from one account to another. Each time a customer he had robbed questioned the balance in his account, the teller claimed a computer error, then replaced the missing money from someone else’s account. This man was caught only because he was a gambler. When re police broke up an illegal gambling operation, his name was in the records.
Some employees use the computer’s power to get revenge(报仇) on employers they consider unfair. Recently, a large insurance company fired its computer-tape librarian for reasons that involved her personal rather than her professional life. She was given thirty day’s notice(辞退,解雇等的预先通知). In those thirty days, she erased all the company’s computerized records.
Most computer criminals have been minor employees. Now police wonder if this is "the tip of the iceberg. "As one official says, "I have a feeling that there is more crime out there than we are catching What we are seeing now is all so poorly done. I wonder what the real experts are doing those who really know how a computer works.\

It is difficult find out computer criminals because（）

点击查看答案&解析