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...