Computers have become so necessary for modern living that it is difficult to believe they are a relatively recent invention. Undoubtedly, they have proved valuable, but they also have disadvantages. For example, they have increased our already large number of crimes. Hacking was the first computer crime that most of us became aware of. By using their computing expertise, hackers can gain unauthorized access to someone else’s computer and make use of the data they find there. They may, for example, find lists of their competitors’ clients and use these lists to build up their own businesses or they may use hacking technology to find out a rival company’s plans. Other hacking activities may be more obviously criminal, because hackers may log on to financial data in someone else’s computer and alter it illegally or use it for fraudulent（欺诈的） purposes. The possibility of serious financial fraud has been greatly increased by the modern practice of purchasing goods through the Internet. Apparently, the use of credit cards to pay for purchases has led to many people being swindled y （骗取）out of a great deal of money. Banks are working hard to improve online security and to provide safeguards for customers, but frauds are working just as hard to improve their techniques of deceiving people. Many computer users worry about their systems being affected by computer viruses. People who introduce these bugs into other people’s computer programs may not intentionally commit a crime but may do so as an act of mischief. The motive does not really matter to people whose data has been deleted or altered or whose files have been corrupted. Computers are part of a highly technical method of working, in which there are constantly new developments. Unfortunately, there is also a constant stream of new developments in the fraud industry associated with them. All computer users must be on their guard.