Computer Security 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 impo