This document defines a computer virus and discusses how viruses spread and the types of damage they can cause. It outlines symptoms of a virus infection and types of viruses like boot sector viruses, macro viruses, and script viruses. The document recommends installing antivirus software from reputable companies, backing up files regularly, being cautious of email attachments, and avoiding unknown programs as ways to prevent virus infections.

2. Introduction
What is computer virus ?
Symtoms
How does it spread?
What a computer virus do ?
Types of computer viruses ?
Prevention from computer virus ?
Antivirus Software
Conclusion

3. INTRODUCTION TO VIRUS
A virus is a
program designed
by a computer
programmer
(malicious hacker)
to do a certain
unwanted
function.

4. What is computer virus ?
Computer virus is a type of destructive
program that can replace itself by making copies of
itself without the knowledge of the user. Computer
virus is a term given to man-made computer software
or system to destroy computer programs or computer.
The virus destroys data, useful application, programs,
and even the operating system. Computer virus hides
themselves in other host files. They are not visible to
us. The viruses can corrupt, delete files and programs.
Computer Viruses affect the computer in
many ways. It can destroy data, files or programs and
cause the system malfunction. The destructive effects
of viruses are different according to their types.

5. Symptoms
 Letter looks like they are falling to the
bottom of the screen.
 The Computer System becomes slow
 The size of available free memory
reduces.
 The hard disk runs out of space.
 The computer does not boot.

6. HOW DOES IT SPREAD?
Computer Viruses spread by attaching
themselves to other computer program
files.
When you exchange a file or pendrive
with a virus, the virus spreads from one
computer to the another.
Viruses also spread when a computer
engineer comes to repair your system and
put his/her diagnostics disks in your PC.

7. WHAT A COMPUTER VIRUS DO?
SLOW DOWN
THE NETWORK
HIJACK YOUR
COMPUTER
STEAL
CONFIDENTIAL
DATA
DELETE DATA
DISPLAY
MESSAGES
DISABLE
HARDWARE
CORRUPT DATA

9. Boot
Sector
Virus
Time
Bomb
Logical
Bomb
Macros
Virus
Script
Virus

10. TIME BOMB
A time bomb is a virus program
that performs an activity when a
certain action has occurred
LOGICAL BOMB
A logical bomb is a destructive
program that performs an activity
when a certain action has
occurred

11. BOOT SECTOR VIRUS
The boot sector virus infects the
information system during the start-up
process.
It tends to create the bad sector of the
hard drive or floppy disk.
The virus infects the system by using
infected diskettes during start up.
The entire computer system becomes
slow by reading the virus from the disk
boot sector.
The examples of such viruses are C-
Brain, Stone, Disk Killer etc.

12. Macros Virus
A macro virus is associated with application
software like word and excel. When opening the
infected document, macro virus is loaded into
main memory and destroys the data stored in
hard disk.
Script Virus
The virus which is developed by using script
language is known as script virus. This virus uses
script language to transfer from one computer to
another. This virus is created by using script
language like VBscript, Javascript. The examples
of such viruses are Readlof.A, Sujim .com.np.

13. Computer viruses
are very harmful to
computer system.
They can destroy
data and
information.
So, computer should
be protected from
viruses.
Protection from virus

14.  Install anti-virus software from a well known, reputed
company and use it regularly.
 Do backup your entire system on a regular basis. Because
some viruses may erase or corrupt files on your hard disk.
 Do not use any pirated software.
 Lock the computer system using password to prevent your
computer from being used by others.
 Do not download any programs from the internet unless
you are confirmed that they are virus free.
 Be careful while checking mail having attached documents.

16. Kespersky Antivirus
Data fellows E-Plot
Mcafee Antivirus
Symantec Norton Antivirus
Bit Defender 2010
Quick Heal Antivirus
ESaSS ThunderBYTE

17. Be aware of the new infections out
there.
Take precaution measures.
Always backup your data.
Keep up-to-date on new Anti virus
software.
Simply avoid programs from unknown
sources.