What is virus?
Computer viruses are small software programs that are designed
to spread from one computer to another and to interfere with
A virus might corrupt or delete data on your computer, use your
e-mail program to spread itself to other computers, or even erase
everything on your hard disk.
Viruses are most easily spread by attachments in e-mail
messages or instant messaging messages. That is why it is
essential that you never open e-mail attachments unless you
know who it's from and you are expecting it.
Viruses can be disguised as attachments of funny images,
greeting cards, or audio and video files. Viruses also spread
through downloads on the Internet. They can be hidden in illicit
software or other files or programs you might download.
To help avoid viruses, it's essential that you keep your computer
current with the latest updates and antivirus tools , stay
informed about recent threats , and that you follow a few basic
rules when you surf the Internet, download files, and open
Once a virus is on your computer, its type or the method it used
to get there is not as important as removing it and preventing
further infection .
A computer virus is a computer program that can copy itself and
infect a computer without permission or knowledge of the user. The
virus may also be purposly planted in order to cause confusion. The
original may modify the copies or the copies may modify themselves,
as occurs in a metamorphic virus . A virus can only spread from one
computer to another when its host is taken to the uninfected computer,
for instance by a user sending it over a network or carrying it on a
removable medium such as a floppy disk , CD , or USB drive .
Additionally, viruses can spread to other computers by infecting files
on a network file system or a file system that is accessed by another
computer. Viruses are sometimes confused with computer worms
and Trojan horses . A worm, however, can spread itself to other
computers without needing to be transferred as part of a host. A
Trojan horse is a file that appears harmless until executed. In contrast
to viruses, Trojan horses do not insert their code into other computer
files. Many personal computers are now connected to the Internet and
to local-area networks, facilitating their spread. Today's viruses may
also take advantage of network services such as the World Wide
Web , e-mail , and file sharing systems to spread, blurring the line
between viruses and worms. Furthermore, some sources use an
alternative terminology in which a virus is any form of selfreplicating malware .
How do I remove a computer virus?
If your computer is infected with a virus, you'll want to remove it as
quickly as possible. A fast way to check for viruses is to use an online
scanner, such as the Microsoft Safety Scanner. The scanner is a free
online service that helps you identify and remove viruses, clean up
your hard disk, and generally improve your computer's performance.
If you're not sure whether your computer has a virus, see How can I
tell if my computer has a virus? to check for some telltale signs. To
try a different online scanner, follow the links to other companies that
provide them on the Windows Security software providers webpage.
To run the Microsoft Safety Scanner
Go to the Microsoft Safety Scanner webpage to download the
Click Download Now, and then follow the instructions on the
If you can't connect to the Internet
If you can't get to the Microsoft Safety Scanner online, try restarting
your computer in safe mode with networking enabled.
To restart in Safe Mode with networking enabled
Restart your computer.
When you see the computer manufacturer's logo, press and hold
the F8 key.
On the Advanced Boot Options screen, use the arrow keys to
highlight Safe Mode with Networking, and then press Enter.
Log on to your computer with a user account that has
Follow the steps above to run the Microsoft Safety Scanner.
General Information About Computer Virus
Different Malware Types
Malware is a general name for all programs that are harmful;
viruses, trojan, worms and all other similar programs.
A computer virus is a program, a block of executable code,
which attach itself to, overwrite or otherwise replace another
program in order to reproduce itself without a knowledge of a
There are a couple of different types of computer viruses: boot
sector viruses, parasitic viruses, multi-partite viruses,
companion viruses, link viruses and macro viruses. These
classifications take into account the different ways in which the
virus can infect different parts of a system. The manner in which
each of these types operates has one thing in common: any virus
has to be executed in order to operate.
Most viruses are pretty harmless. The user might not even notice
the virus for years. Sometimes viruses might cause random
damage to data files and over a long period they might destroy
files and disks. Even benign viruses cause damage by occupying
disk space and main memory, by using up CPU processing time.
There is also the time and expense wasted in detecting and
A Trojan Horse is a program that does something else that the
user thought it would do. It is mostly done to someone on
purpose. The Trojan Horses are usually masked so that they
look interesting, for example a saxophone.wav file that interests
a person collecting sound samples of instruments. A Trojan
Horse differs from a destructive virus in that it doesn't
reproduce. There has been a password trojan out in AOL land
(the American On Line). Password30 and Pasword50 which
some people thought were wav. files, but they were disguised
and people did not know that they had the trojan in their
systems until they tried to change their passwords.
According to an administrator of AOL, the Trojan steals
passwords and sends an E-mail to the hackers fake name and
then the hacker has your account in his hands.
A worm is a program which spreads usually over network
connections. Unlike a virus which attach itself to a host program,
worms always need a host program to spread. In practice, worms are
not normally associated with one person computer systems. They are
mostly found in multi-user systems such as Unix environments. A
classic example of a worm is Robert Morrisis Internet-worm 1988.
Other types of Virus
Bacteria, also known as rabbits, are programs that do not
directly damage the the system. Instead they replicate
themselves until they monopolize CPU, memory or disk space.
This constitutes a denial of service attack.
A bomb is actually a type of Trojan horse that can be used to
release a virus or bacteria. Bombs work by causing an
unauthorized action at a specified date, time or when a particular
condition occurs. There are two types of bombs; logic and time.
Logic bombs are set to go off when a particular event occurs.
Time bombs go off at a specified time, date or after a set amount
of time elapses.
Salamis cut away tiny pieces of data. They can be particularly
dangerous as the damage they do is small and can be attributed
to some truncation of the system. It is possible for a salami to do
a great deal of damage before it is found.
HOW VIRUSES ACTIVE?
We are always afraid that viruses do something harmful to files when
they get active, but not all the viruses activate. Some viruses just
spread out, but when viruses activate they do very different things.
Might play a part of melody or play music in the background, show a
picture or animated picture, show text, format hard disk or do changes
As an example, in one unnamed company: over a long period of time,
the files in a server were corrupted just a bit. So backup copies were
taken from the corrupted files. And after they noticed that something
was wrong, it was too late to get back the data from the backups. That
kind of event is the worst that can happen for the uses.
There are lots of viruses in the world and new viruses are
coming up every day. There are new anti-virus programs and
techniques developed too. It is good to be aware of viruses and
other malware and it is cheaper to protect you environment from
them rather then being sorry.
There might be a virus in your computer if it starts acting
differently. There is no reason to panic if the computer virus is
It is good to be a little suspicious of malware when you surf in
the Internet and download files. Some files that look interesting
might hide a malware.
A computer virus is a program that reproduces itself and its
mission is to spread out. Most viruses are harmless and some
viruses might cause random damage to data files.
A trojan horse is not a virus because it doesn't reproduce. The
trojan horses are usually masked so that they look interesting.
There are trojan horses that steal passwords and formats hard