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What is a computer virus
How a computer virus spreads
First computer virus
Types of computer viruses
How to detect a virus
How to prevent virus
I would like to express my special thanks of gratitude to
my teacher ms.Tasneem mam as well as our principal
who gave me the golden opportunity to do this wonderful
project on the topic types of viruses, which also helped me
in doing a lot of Research and i came to know about so
many new things
I am really thankful to them.
Secondly i would also like to thank my parents and friends
who helped me a lot in finishing this project within the
I am making this project not only for marks but to also
increase my knowledge.
THANKS AGAIN TO ALL WHO HELPED ME.
What is a computer
A computer virus is a type of malware that, when
executed, replicates by inserting copies of itself (possibly
modified) into other computer programs, data files, or the boot
sector of the hard drive; when this replication succeeds, the
affected areas are then said to be "infected". Viruses often
perform some type of harmful activity on infected hosts, such as
stealing hard disk space or CPU time, accessing private
information, corrupting data. However, not all viruses carry a
destructive payload or attempt to hide themselves.
The vast majority of viruses (over 99%) target systems
running Microsoft Windows, employing a variety of mechanisms
to infect new hosts, and often using complex anti-detection/stealth
strategies to evade antivirus software.
Computer viruses currently cause billions of dollars worth of
economic damage each year, due to causing systems failure,
wasting computer resources, corrupting data, increasing
maintenance costs, etc.
How a computer virus
For a computer virus to spread through a computer system, or
network, it must be activated. This means that the file that
contains the virus must be opened, or executed in order for the
virus to come to life. After it gets activated, these viruses look for
certain programs to infect. The main and the important that you
must note is that, all viruses seem to do well is duplicate
themselves within the programs they find, and this is the main
reason as to how they spread well.
1. Email attachments.
2. Rogue Websites.
3. Networks- If your computer is connected to a home network or
if your work computer is part of a larger network, you may find
yourself with an infection through no fault of your own.
4. Infected hard disks.
5. Hackers/fake Anti Virus Software
6. From Mobile Devices.
7. Friends and Relatives.
First computer virus
Brain is the industry standard name for a computer virus that was
released in its first form in January 1986 and is considered to be
the first computer virus for MS-DOS. It infects the boot sector of
storage media formatted with the DOS File Allocation Table (FAT)
file system. Brain was written by two brothers, Basit Farooq Alvi
and Amjad Farooq Alvi from Lahore, Pakistan.
Brain affects the IBM PC computer by replacing the boot sector of
a floppy disk with a copy of the virus. The real boot sector is
moved to another sector and marked as bad. Infected disks
usually have five kilobytes of bad sectors.
Types of computer
A program written to deliver a malicious program that may then
cause destruction to your computer. A Trojan horse is delivered
by someone or hidden within another program that may seem
A program written to monitor your actions on a computer. A
common type of spyware is a key-logger program. This program
can record every key stroke and mouse click you make. Spyware
can be delivered via a Trojan horse program.
Adware is a form of malware. One word - pop-ups. Adware is
designed to pop up advertisements. Adware can be very
Just a nasty little program to cause slowness in a network. A
worm will replicate itself and spread from computer to computer.
Worms are commonly spread through email attachments.
Boot Sector Virus
Not so common anymore, but they were nasty little programs that
got loaded into your master boot record. Most commonly spread
by floppy disks. These viruses could then launch themselves
before your operating system even loaded.
A virus written to execute at a later date or upon an action
performed. These programs lay dormant until an event occurs.
A virus that will over take your web browser and automatically
redirect you to another website.
File Infector Virus
A virus that lives within a file, typically a .exe file. When the file is
executed, it will then run its nasty code.
A virus written to change itself in order to evade virus detection.
A virus that hides itself inside of macros used by programs such
as Microsoft Excel.
Web Scripting Virus
A virus that hides within a website. Some are put there on
purpose, some get injected into websites that are not properly
How to detect a
Virus (signs of virus being infected)
Signs of an infected computer can be numerous depending on
which virus your computer is infected with.
1. My computer speaks to me.
There are all types of pop-ups and messages on the desktop
either advertising things, saying that the PC is infected and needs
2. My computer is running extremely slowly.
This could be a symptom of many things, including infection by a
virus. If it has been infected by a virus, worm or Trojan, among
other things, which are running on the computer, they could be
running tasks that consume a lot of resources.
3. Applications won't start.
Sometimes another program might even run. As in the previous
case, this could be another type of problem, but at the very least
it's a symptom that tells you that something is wrong.
4. I cannot connect to the Internet or it runs very slowly.
Loss of Internet communication is another common symptom of
infection, although it could also be due to a problem with your
service provider or router.
5. When I connect to the Internet, all types of windows open
or the browser displays pages I have not requested.
This is another certain sign of infection. Many threats are
designed to redirect traffic to certain websites against the user’s
will, and can even spoof Web pages.
6. My antivirus has disappeared, my firewall is disabled.
Another typical characteristic of many threats is that they disable
security systems installed on computers. Perhaps if one thing
shuts down it might just be a specific software failure; but if all
your security components are disabled.
7. Library files for running games, programs, etc. have
disappeared from my computer.
Once again, this could be a sign of infection, although it could
also be down to incomplete or incorrect installation of programs.
To check for viruses, scan your computer with an antivirus
program. New viruses appear every day, so keeping your
antivirus program updated is important.
How to prevent
1. Install a reliable antivirus program
From the first moment you turn your computer on, you should
have a trusted anti virus program by your side. Even if you have a
machine that isn’t hooked up to the Internet, a reliable anti virus
program is a low cost and common sense addition to any
2. Avoid suspicious websites.
A good virus protection program will alert you when you visit a
website that attempts to install or run a program on your
computer. Many less than reputable adult websites do this, so if
you get a warning, don’t go back, you may end up with a bug you
can’t get rid of.
3. Never Open Email Attachments Without Scanning Them First.
The most common way viruses are spread throughout the
Internet is still via email. Some attachments, like pictures, now
display in emails and don’t require an attachment to be manually
opened, but other documents do.
4. Set up Automatic Scans
Many of the top anti virus programs, as well as the best anti-
spyware programs, now have settings that will let them
automatically run during down times or in the middle of the night.
5. Know What To Look .
Even if you are just a casual computer user, you should have an
idea of how your machine operates, what normal pop up windows
look like and what popular viruses are out there, that way, when
your computer begins exhibiting tell tale signs, you’ll know.
6. Stay Away From Cracked Software.
It is so secret that you can download illegal, cracked versions of
some programs online. As tempting as it may be, these files are
almost always infested with advanced and difficult to detect bugs.
Play it safe and get your software from the source.
7. Install a Firewall
A firewall is a program that screens incoming Internet and