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What is a computer virus?
Computer program
пЃ® Replicating
пЃ® Problematic "Event"
пЃ® Types
пЃ® Detection and prevention
пЃ®
1
What is a computer virus?
A computer virus is an executable program. By definition, a
virus program is able to replicate itself. This means that the
virus multiplies on a computer by making copies of itself.
This replication is intentional; it is part of the virus program.
2
What is a computer virus?
A virus can be introduced to a computer system along with
any software program. For Internet users, this threat can come
from downloading files through FTP (file transfer protocol).
When a virus is introduced to a computer system, it can attach
itself to, or sometimes even replace, an existing program.
Thus, when the user runs the program in question, the virus is
also executed.
This usually happens without the user being aware of it.
3
What is a computer virus?
A virus program contains instructions to initiate some sort of
"event" that affects the infected computer. Each virus has a
unique event associated with it. These events and their effects
can range from harmless to devastating. For example:
пЃ® An
annoying message appearing on the computer screen.
пЃ®
Reduced memory or disc space.
пЃ®
Modification of data.
пЃ®
Files overwritten or damaged.
пЃ®
Hard drive erased.
4
What is a computer virus?
There are many types of computer viruses including file
viruses, boot sector viruses and Trojan Horse programs.
File virus - Most viruses fall into this category. A virus
attaches itself to a file, usually a program file.
пЃ®
Boot sector virus - These viruses infect floppy and hard
drives. The virus program will load first, before the operating
system.
пЃ®
Trojan Horse - These programs appear to be something
other than what they are, for example a "virus" that is
disguised as a legitimate software program. Some virus
experts do not classify Trojan Horse programs as true viruses,
because they generally don't replicate.
пЃ®
5
What is a computer virus?
Often, a user isn't aware that his or her computer is infected with
a virus until the virus executes its unique event, such as
displaying an unusual message or damaging a file. It is hard for
people to detect viruses because they usually don't display
symptoms prior to the event taking place.
However, some viruses will provide early clues that they exist,
such as:
Changes in file or date stamp.
пЃ® Longer times to load programs.
пЃ® Slower system operation.
пЃ® A program fails to start.
пЃ® An unusual amount of disk activity (the floppy or disk
drive runs for no apparent reason).
пЃ®
6
What is a computer virus?
Using anti-virus tools makes detecting and eradicating viruses an
easier task. There are many types of anti-virus software,
employing several technologies. A common type of anti-virus
tool is a "scanner".
Scanners examine every file on a specific disc drive, looking for
known virus "signatures". Every virus has a unique signature,
which is a string of software code. Drawbacks to scanners
include their inability to detect new viruses, and the requirement
that the user determines when to initiate the virus scanning
process.
Other types of anti-virus tools include those that will run
continuously on a system, and those that will run every time the
machine is booted.
7
What is a computer virus?
In Summary:
A computer virus is an executable program that is able to replicate
itself. Each virus contains instructions to initiate a unique,
problematic event on the infected computer. The effects of these
events can range from annoying to potentially devastating.
A common type of virus is a file virus, which attaches itself to an
existing program. When the program is run, the virus is also
executed. Internet users can unknowingly download a software
program that contains a virus.
Other virus types include boot sector viruses and Trojan Horse
programs which some experts do not classify as true viruses. Antivirus tools can help a user to detect and eradicate viruses before
they have an effect on an infected computer.
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