Computer

About two hundred years before, the word "computer" started  


to appear in the dictionary. Some people even didn't know what is


a computer. However, most of the people today not just knowing


what is a computer, but understand how to use a computer.


Therefore, computer become more and more popular and


important to   our society. We can use computer everywhere and


they are very useful and helpful to our life. The speed and


accuracy of computer made people felt confident and reliable.


Therefore, many important information or data are saved in the


computer. Such as your diary, the financial situation of a oil


company or some secret intelligence of the military department. A


lot of important information can be found in the memory of


computer. So, people may ask a question: Can we make sure that


the information in the computer is safe and nobody can steal it


from the memory of the computer?


Physical hazard is one of the causes of destroying the data


in the computer. For example, send a flood of coffee   toward a


personal computer. The hard disk of the computer could be


endangered by the flood of coffee. Besides, human caretaker of


computer system can cause as much as harm as any physical hazard.


For example, a cashier in a bank can transfer some money from one


of his customer's account to his own account. Nonetheless, the


most dangerous thief are not those who work with computer every


day, but youthful amateurs who experiment at night --- the


hackers.


The term "hacker "may have originated at M.I.T. as students'


jargon for classmates who labored nights in the computer lab. In


the beginning, hackers are not so dangerous at all. They just


stole computer time from the university. However, in the early


1980s, hackers became a group of criminals who...