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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 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
copied 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 new technology called biometric device to identify
the person who wants to use your computer. Biometric devices are
instrument that perform mathematical analyses of biological
characteristics. For example, voices, fingerprint and geometry of the
hand can be used for identification. Nowadays, many computer centers,
bank vaults, military installations and other sensitive areas have
considered to use biometric security system. It is because the rate of
mistaken acceptance of outsiders and the rejection of authorized insiders
is extremely low.
	Individuality of vocal signature is one kind of biometric
security system. The main point of this system is voice verification. The
voice verifier described here is a developmental system at American
Telephone and Telegraph. Only one thing that people need to do is
repeating a particular phrase several times. The computer would sample,
digitize and store what you said. After that, it will built up a voice
signature and make allowances for an individual's characteristic
variations. The theory of voice verification is very simple. It is using
the characteristics of a voice: its acoustic strength. To isolate
personal characteristics within these fluctuations, the computer breaks
the sound into its component frequencies and analyzes how they are
distributed. If someone wants to steal some information from your
computer, the person needs to have a same voice as you and it is
impossible.
	Besides using voices for identification, we can use fingerprint
to verify a person's identity because no two fingerprints are exactly
alike. In a fingerprint verification system, the user places one finger
on a glass plate; light flashes inside the machine, reflects off the
fingerprint and is picked up by an optical scanner. The scanner transmits
the information to the computer for analysis. After that, security
experts can verify the identity of that person by those information.
	Finally, the last biometric security system is the geometry of
the hand. In that system, the computer system uses a sophisticated
scanning device to record the measurements of each person's hand. With an
overhead light shining down on the hand, a sensor underneath the plate
scans the fingers through the glass slots, recording light intensity from
the fingertips to the webbing where the fingers join the palm. After
passing the investigation of the computer, people can use the computer or
retrieve data from the computer.
	Although a lot of security system have invented in our world,
they are useless if people always think that stealing information is not
a serious crime. Therefore, people need to pay more attention on computer
crime and fight against those hackers, instead of using a lot of computer
security systems to protect the computer.
       Why do we need to protect our computers ?
	It is a question which people always ask in 18th century. However,
every person knows the importance and useful of a computer security 
system.
     In 19th century, computer become more and more important and helpful.
You can input a large amount of information or data in a small memory chip
of a personal computer. The hard disk of a computer system is liked a bank.
It contained a lot of costly material. Such as your diary, the financial
situation of a trading company or some secret military information.
Therefore, it just like hire some security guards to protect the bank. A
computer security system can use to prevent the outflow of the
information in the national defense industry or the personal diary in your
computer.
	Nevertheless, there is the price that one might expect to pay for
the tool of security: equipment ranging from locks on doors to
computerized gate-keepers that stand watch against hackers, special
software that prevents employees to steal the data from the company's
computer. The bill can range from hundreds of dollars to many millions,
depending on the degree of assurance sought.
	Although it needs to spend a lot of money to create a computer
security system, it worth to make it. It is because the data in a computer
can be easily erased or destroyed by a lot of kind of hazards. For example,
a power supply problem or a fire accident can destroy all the data in a
computer company. In 1987, a computer centre inside the Pentagon, the US
military's sprawling head quarters near Washington, DC., a 300-Watt light
bulb once was left burning inside a vault where computer tapes were stored.
After a time, the bulb had generated so much heat that the ceiling began
to smelt. When the door was opened, air rushing into the room brought the
fire to life. Before the flames could be extinguished, they had spread
consume three computer systems worth a total of $6.3 million.
	Besides those accidental hazards, human is a great cause of the
outflows of data from the computer. There have two kind of people can go
in the security system and steal the data from it. One is those trusted
employee who is designed to let in the computer system, such as
programmers, operators or managers. Another kind is those youth amateurs
who experiment at night ---- the hackers.
	Let's talk about those trusted workers. They are the groups who
can easily become a criminal directly or indirectly. They may steal the
information in the system and sell it to someone else for a great profit.
In another hand, they may be bribed by someone who want to steal the data.
It is because it may cost a criminal far less in time and money to bride a
disloyal employee to crack the security system.
	Beside those disloyal workers, hacker is also very dangerous. The
term "hacker" is originated at M.I.T. as students' jargon for classmates
who doing computer lab in the night. In the beginning, hackers are not so
dangerous at all. They just stole some hints for the test in the
university. However, in early 1980s, hacker became a group of criminal who
steal information from other commercial companies or government
departments.
       What can we use to protect the computer ?
	We have talked about the reasons of the use of computer security
system. But what kind of tools can we use to protect the computer. The
most common one is a password system. Password are a multi-user computer
system's which usual used for the first line of defense against intrusion.
A password may be any combination of alphabetic and numeric characters, to
maximum lengths set by the e particular system. Most system can
accommodate passwords up to 40 characters. However, a long passwords can
be easily forget. So, people may write it down and it immediately make a
security risk. Some people may use their first name or a significant word.
With a dictionary of 2000 common names, for instance, a experienced hacker
can crack it within ten minutes.
	 Besides the password system, card-keys are also commonly used.
Each kind of 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 criminal. Three types of card usually
used. They are magnetic watermark, Optical memory card and Smart card.
	However, both of the tools can be easily knew or stole by other
people. Password are often forgotten by the users and card-key can be
copied or stolen. Therefore, we need to have a higher level of computer
security system. Biometric device is the one which have a safer protection
for the computer. It can reduce the probability of the mistaken acceptance
of outsider to extremely low. Biometric devices are instrument that
perform mathematical analyses of biological characteristics. However, the
time required to pass the system should not be too long. Also, it should
not give inconvenience to the user. For example, the system require people
to remove their shoes and socks for footprint verification.
	Individuality of vocal signature is one kind of biometry security
system. They are still in the experimental stage, reliable computer
systems for voice verification would be useful for both on-site and remote
user identification. The voice verifier described here is invented by the
developmental system at American Telephone and Telegraph. Enrollment would
require the user to repeat a particular phrase several times. The computer
would sample, digitize and store each reading of the phrase and then, from
the data, build a voice signature that would make allowances for an
individual's characteristic variations.
	Another biometric device is a device which can measuring the act
of writing. The device included a biometric pen and a sensor pad. The pen
can converts a signature into a set of three electrical signals by one
pressure sensor and two acceleration sensors. The pressure sensor can
change in the writer's downward pressure on the pen point. The two
acceleration sensor can measure the vertical and horizontal movement.
	The third device which we want to talk about is a device which can
scan the pattern in the eyes. This device is using an infrared beam which
can scan the retina in a circular path. The detector in the eyepiece of
the device can measure the intensity of the light as it is reflected from
different points. Because blood vessels do not absorb and reflect the same
quantities of infrared as the surrounding tissue, the eyepiece sensor
records the vessels as an intricate dark pattern against a lighter
background. The device samples light intensity at 320 points around the
path of the scan , producing a digital profile of the vessel pattern. The
enrollment can take as little as 30 seconds and verification can be even
faster. Therefore, user can pass the system quickly and the system can
reject those hackers accurately.
	The last device that we want to discuss is a device which can map
the intricacies of a fingerprint. In the verification system, the user
places one finger on a glass plate; light flashes inside the machine ,
reflect off the fingerprint and is picked up by an optical scanner. The
scanner transmits the information to the computer for analysis.
	Although scientist have invented many kind of computer security
systems, no combination of technologies promises unbreakable security.
Experts in the field agree that someone with sufficient resources can
crack almost any computer defense. Therefore, the most important thing is
the conduct of the people. If everyone in this world have a good conduct
and behavior, there is no need to use any complicated security system to
protect the computer.