Computer virus
is a hostile program that generally replicates itself and infests other files.
These malicious programs are developed by computer hackers and disgruntled
programmers.
They are
usually written in assembly language or high-level languages like 'C'. Some of
these may be harmless as they display some messages or playa tune. But most of
the viruses are highly
harmful to
computer systems. The harm done to the computer system depends on the type of
virus and frequency of its strike.
Viruses are
quite common in DOS and Windows environments. They normally spread through
floppy diskettes carrying pirated software. With microcomputers joining the
Internet, the spread of virus is swift and wide through this global network.
A worm is a
program that copies itself repetitively into computer memory or disk drives
until the memory or disk space is
exhausted. It can cause the computer to stop functioning as it runs out of
memory to load and run applications. Worm is an autonomous agent capable of
propagating itself without the help of other programs. Most worms disrupt
services and create problems for system management. Some worms scan passwords
and other sensitive information and pass them to the attacker.
Some worms can
install viruses that can cause destruction of data or damage to systems.
Origin
of Computer Virus
John Von
Neumann first suggested the concept of self replicating programs in 1950. A few
of the programmers at AT&T started working on self-replicating programs as
a game. The game involved writing code to destroy other's code in the computer
memory and the one who has maximum number of lines of code wins the game. The
game was kept a secret and was never released for the public. Later, Ken
Thomson, co-author of UNIX encouraged programmers to write programs like the
one at AT
&T. Early viruses were developed by hackers to enter other's systems.
Types
of Viruses
There are
thousands of viruses and several thousand variations of these viruses. Some of
the commonly found computer viruses are:
1.
Stone Marijuna Virus
This affects
boot sector of floppy diskettes and the master boot record containing partition
table on hard disks. It displays a message "Your PC is stoned".
2.
The Vienna-648 Virus
This virus
infects files with size larger than 10 bytes. It usually infects' .com' files
and increases infected file size by 648 bytes.
3.
Joshy
This virus is
of Indian origin and affects boot sector of floppy diskettes and master boot
record of hard disks. It becomes active on the 5th of
January every year and the computer system hangs when the virus is active. If
the message "Happy birth day Joshy" is typed, the system starts
functioning normally.
4.
Dark Avenger Virus
It infects
files with size larger than 1800 bytes and is very difficult to remove. It
affects' .com' and' .exe' files. It increases the size of infected files by
1800 bytes, reduces RAM by 4 KB and displays the message "Eddie Lives
Somewhere in Time".
5.
Stealth Viruses
Stealth viruses
are hard to detect and are very dangerous. They include 512A, Holocaust, V-2000
Whale, Murphy and Michael Angelo. The Michael Angelo virus wipes out data on
hard disk on Friday the 6th of March, the birthday of artist Michael Angelo.
6.
Flush Virus
It is a
memory-resident virus that infects' .com' and' .exe' files.
7.
Jerusalem Virus
It affects'
.exe' and' .com' files. It increases the size of '.exe' files by 1808 bytes and
that of' .com' files by 1813 bytes.
8. Perfume
It infects
'.com' file and increases its size by 765 bytes. It shoots a question and if
the number 4711 (the name of a German perfume) is typed, it functions normally.
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