Viruses, remove virus, viruses catalog
What is a virus?
A virus is a program that
can infect or contaminate other programs and is
often detrimental to computer data or system integrity.
Viruses are most frequently spread by opening infected
email attachments. The virus can then send itself
to everyone listed in the recipient's email address
book. Some viruses are spread through Internet downloads,
while others are spread through infected disks.
There are thousands and thousands of known viruses,
and new virus strains continue to show up regularly.
The rate of virus infection is rapidly increasing.
History of computer viruses
program called "Elk Cloner" is credited
with being the first computer virus to appear "in
the wild" -- that is, outside the single computer
or lab where it was created. Written in 1982 by
Rich Skrenta, it attached itself to the Apple DOS
3.3 operating system and spread by floppy disk.
This virus was originally a joke, created by the
high school student and put onto a game. The game
was set to play, but release the virus on the 50th
time of starting the game. Only this time, instead
of playing the game, it would change to a blank
screen that read a poem about the virus named Elk
Cloner. The computer would then be infected.
The first PC virus was a boot sector virus called
(c)Brain, created in 1986 by two brothers, Basit
and Amjad Farooq Alvi, operating out of Lahore,
Pakistan. The brothers reportedly created the virus
to deter pirated copies of software they had written.
However, analysts have claimed that the Ashar virus,
a variant of Brain, possibly predated it based on
code within the virus.
Before computer networks became widespread, most
viruses spread on removable media, particularly
floppy disks. In the early days of the personal
computer, many users regularly exchanged information
and programs on floppies. Some viruses spread by
infecting programs stored on these disks, while
others installed themselves into the disk boot sector,
ensuring that they would be run when the user booted
the computer from the disk.
Traditional computer viruses emerged in the 1980s,
driven by the spread of personal computers and the
resultant increase in BBS and modem use, and software
sharing. Bulletin board driven software sharing
contributed directly to the spread of Trojan horse
programs, and viruses were written to infect popularly
traded software. Shareware and bootleg software
were equally common vectors for viruses on BBS's.
Within the "pirate scene" of hobbyists
trading illicit copies of commercial software, traders
in a hurry to obtain the latest applications and
games were easy targets for viruses.
Since the mid-1990s, macro viruses have become common.
Most of these viruses are written in the scripting
languages for Microsoft programs such as Word and
Excel. These viruses spread in Microsoft Office
by infecting documents and spreadsheets. Since Word
and Excel were also available for Mac OS, most of
these viruses were able to spread on Macintosh computers
as well. Most of these viruses did not have the
ability to send infected e-mail. Those viruses which
did spread through e-mail took advantage of the
Microsoft Outlook COM interface.
Categories of viruses
This is the most common type of virus. A file-infecting
virus attaches itself to an executable program file
by adding its own code to the file. An executable
program file can be run and has an .EXE extension.
The virus code is usually added in such a way that
it escapes detection. When the infected file is
run, the virus can attach itself to other executable
files. Files infected by this type of virus usually
have a .COM, .EXE, or .SYS extension. Damage to
data can occur when the virus is triggered. A virus
can be triggered when an infected file is executed,
or when a particular environment setting is met
(such as a specific system date).
When a computer boots (or starts), it looks to the
boot sector of the hard disk before loading the
operating system or any other startup files. A boot-sector
virus is designed to replace the information in
the hard disk's boot sectors with its own code.
When a computer is infected with a boot-sector virus,
the virus' code is read into memory before anything
else. Once the virus is in memory, it can replicate
itself onto any other disks that are used in the
Trojan Horse Programs
As a legitimate program such as a game or utility,
but once it is executed, it can destroy or scramble
data. A Trojan horse program can contain viruses,
but is not a virus itself.
A worm is an independent program that replicates
itself, crawling from machine to machine across
network connections. It often clogs networks as
it spreads, often via e-mail.
How do viruses spread?
Viruses are most frequently
spread by opening infected email attachments. The
virus can then send itself to everyone listed in
the recipient's email address book. Some viruses
are spread through Internet downloads, while others
are spread through infected disks.
How can i prevent computer viruses?
You must buy and run quality software
on all your computers to protect you from viruses,
spyware, and other potentially harmful applications.
There is no budget solution, you must do the following
or it is likely your computer will be hit by a virus
and your work/data will be lost:
Get good anti virus software e.g. one of the below.
Regularly update your 'virus definitions' e.g. once
Email Attachments: BEWARE OF ATTACHMENTS. Do not
open email attachments that you are not expecting.
Viruses come with some very nasty messages to trick
you into opening the attachement e.g. "Your
email account has been cancelled, see attachment
for details". Even worse, the virus looks like
it comes from an email address you recognise e.g.
from admin@yourDomain.com (where 'your domain' is
the domain name that you use). Virus attachments
tend to have the following 'file extension': .exe,
.pif. If you receive a .zip attachment and open
it - make sure it doesn't contain a file with one
of those extensions. Do not open attachments you
haven't requested, even if they appear to be from
people you know.
|Everyone heard the adage "The
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