1. Prepared By :
Binisha Tamang
Shree Rudrayanee Secondary School
Lalitpur, Nepal

2. A computer virus is a program that can copy
itself and infect a computer without the
permission or knowledge of the user.

3.  Boot sector virus
 File or Program virus
 Macro virus
 Multipartite virus
 Stealth virus

4.  Boot sector virus replace or implant themselves
in the boot sector, the area of the hard drive (or
any other disk) accessed when you first turn on
your computer. This kind of virus can prevent
you from being able to boot your hard disk. For
example:
 Danish Boot
 Brain
 Disk killer
 Michelangelo

5.  File viruses infect application programs. They
may attach themselves to any executable file,
usually .COM and .EXE files. An application
program infector takes control after the initial
use of the infected program For example:
 Acid Rain
 Alien.298
 Crazy A

6.  Macro viruses are written by using a simplified
macro programming language. These viruses
affect a Microsoft office document created
using MS-Word, MSExcel, MSAccess, etc. The
viruses can spread if the infected document is
open in another computer. For example:
 Melissa
 Word Concept

7.  Multipartite viruses can infect both application
programs and the boot sector of a disk. They
infect program files and when the infected
program is executed; these viruses infect boot
record. Next time, The virus from the boot
record loads in the memory and then starts
infecting other program files on the disk. For
example:
 Invader
 File
 Tequila

8.  Stealth viruses actively hide themselves from
antiviral software by either masking the size of
the file that they hide in or temporarily
removing itself from the infected file and
placing a copy of itself in another location on
the drive. For example:
 Frodo
 Joshi
 Whale

9.  Booting processing becomes slow
 Size of files may be changed
 Location of file may be changed
 Computer gives unnecessary message and
produces sounds

10.  Internet
 Email
 Infected files
 Infected removable storage devices
 Pirated software

11.  Programs take a longer time to load. Memory-
resident operations take a lot of time to start.
 A change occurs in dates and time of saved
files.
 Hard disk is suddenly accessed without a
logical reason.
 Viruses increases the use of disk space and
growth in file size. They attach themselves to
many files.
 Unnecessary massages are display on the
monitor.

12.  Scan downloaded files of the internet before
copying to your computer.
 Use a good antivirus program to scan floppy
disks before copying files. Recommended once
are Total AV, Norton Antivirus and McAfee.
 Do not install pirated software.
 Scan your computer system and removable
storage devices before use.