Protecting A 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 steal
information from other peoples\' computer.

For preventing the hackers and other criminals, people need to set up a good
security system to protect the data in the computer. The most important thing is
that we cannot allow those hackers and criminals entering our computers. It
means that we need to design a lock to lock up all our data or using
identification to verify the identity of someone seeking access to our computers.

The most common method to lock up the data is using a password system.
Passwords are a multi-user computer system\'s usual first line of defense against
hackers. We can use a combination of alphabetic and number characters to form
our own password. The longer the password, the more possibilities a hacker\'s
password-guessing program must work through. However it is difficult to remember
a very long passwords. So people will try to write the password down and it may
immediately make it a security risk. Furthermore, a high speed password-guessing
program can find out a password easily. Therefore, it is not enough for a
computer that just have a password system to protect its data and memory.

Besides password system, a computer company may consider about the security
of its information centre. In the past, people used locks and keys to limit
access to secure areas. However, keys can be stolen or copies easily. Therefore,
card-key are designed to prevent the situation above. Three types of card-keys
are commonly used by banks, computer centers and government departments. Each of
this card-keys can employ an identifying number or password that is encoded in
the card itself, and all are produced by techniques beyond the reach of the
average computer criminals. One of the three card-key is called watermark
magnetic. It was inspired by the watermarks on paper currency.The card\'s
magnetic strip have a 12-digit number code and it cannot be copied. It can store
about two thousand bits in the magnetic strip. The other two cards have the
capability of storing thousands of times of data in the magnetic strip. They are
optical memory cards (OMCs) and Smart cards. Both of them are always used in the
security system of computers.

However, it is not enough for just using password system and card-keys to
protect the memory in the computer. A computer system also need to have a
restricting program to verify the identity of the users. Generally, identity can
be established by something a person knows, such as a password or something a
person has, such as a card-key. However, people are often forget their
passwords or lose their keys. A third method must be used. It is using something
a person has --- physical trait of a human being.

We can use a