●Computer viruses
A “computer virus” is a malicious program that is created for purposes
such as intruding into a computer without the user’s knowledge to destroy
data within the computer, or to spread the virus to other computers. It poses the greatest threat upon usage of information systems and the Internet.
A computer virus usually has a life cycle of “infection”, “dormancy”,
and “appearance of symptoms.”
Infection
No symptoms
appear until certain
conditions are met
Causes the
destruction of
programs or data, or
triggers abnormal
computer operations
Reference
BOT
A “BOT” is a newer type of computer virus created for the purpose of using a
computer for malicious purposes. Once
a computer is infected with a BOT, a
third party with a malicious intent can
manipulate the computer and cause serious damage through acts of nuisance
such as e-mail bombs and DoS (Denialof-Service) attacks. The name comes
from manipulating an infected computer
as if it were a “robot.”
Reference
Spyware
[Type of virus by symptoms]
Type
Symptoms
Program destruction
Causes destruction to the OS as the basic software, or causes
destruction to application software.
Data destruction
Causes destruction to data such as files on auxiliary storage
devices.
Screen display
destruction
Suddenly displays objects on the screen of the display such as
pictures, graphics, or characters.
Specific date/time
message output
Causes symptoms that lower the performance or cause the destruction of files, only when the computer is operated on a specific date/time.
[Type of virus by infection object]
Type
Symptoms
Boot sector virus
Infects the location that stores the programs that are executed
on system launch. Infection is dependent on the OS and type of
machine.
Program virus
Infects other programs during the program execution. Infection
is dependent on the OS and type of machine.
Macro virus
Infects files that are created using applications such as word
processing or spreadsheet software. Infection occurs when the
file is opened. Infection is not dependent on the OS and type of
machine as long as the macro framework is the same.
●Port scan
A “port scan” is the process of scanning a computer to look for open port
numbers. If an open port number is found, it is exploited for intrusion purposes or to block services that use the open port number.
“Spyware” broadly refers to software
that sends personal or other information
from within a computer to the Internet.
Users are often unaware that they have
spyware installed on their computer,
which can lead to serious damage.
Technology element
The types of computer viruses are summarized below.
“Malware” broadly refers to software
that has a malicious intent. Computer
viruses are a common example of malware.
Chapter 9
Infection occurs
when the virus is
copied to other
programs
Appearance
of symptoms
Dormancy
Reference
Malware
Reference
Stealth virus
A “stealth virus” is a type of virus that
attempts to conceal itself so that it is
hard to find the infection.
Reference
Worm
A “worm” is a program that continues to
replicate itself when an infected computer is connected to a network. The
spread of damage depends on the network load.
Reference
Trojan horse
A “Trojan horse” is a program that masquerades as a utility or other useful program, but performs unauthorized
processing when the program is executed. The unauthorized processing
can include the destruction of data within the computer, or the automatic sending of keystroke information. As it does
not self-replicate on infection, it is technically not a computer virus.
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