This document defines and describes different types of computer viruses. It begins by defining a computer virus as a program that installs itself on a computer without permission and runs against the user's wishes. It then lists and describes 7 main types of viruses: 1) File infector viruses infect files with .exe or .com extensions and overwrite the infected file. 2) Boot sector viruses infect storage devices like floppy disks and are able to infect when used to boot a computer. 3) Master boot record viruses replace the master boot record with their own code and run when a computer boots up.

1. virus
Prepared by:-
Rauhl kundu
6th sem,IT

2. Content
 Definition of virus
 Types of virus

3. Definition of virus
 A computer virus is a program or piece
of code that is loaded onto your
computer without your knowledge &
runs against your wishes.
 Viruses can also replicate themselves.
 All computer viruses are man-made.

5. Type of viruses
1. File infector virus
2. Boot sector virus
3. Master boot record virus
4. Multi-partite virus
5. Macro virus
6. Script virus
7. Companion virus

6. 1) File infector virus
It infects files with .exe or .com
extensions.
When the infected file is accessed or
executed, it may be partially or
completely overwritten by the virus.

7. 1) File infector virus
A file infecting virus may be known as
a file infector.
After memory is infected, any non-
infected executed that runs becomes
infected.
E.g.:- Jerusalem & cascade.

8. 2) Boot sector virus
 It is a computer virus that infects a
storage devices floppy/MBR.
 A boot sector virus is able to infect a
computer only if the virus is used to
boot up the computer.
 E.g.-disk killer, stoned, michelangelo

9. 3) Master Boot record virus
 Similar to boot sector virus.
 An MBR virus is common type of virus
that replaces the MBR with it own
code.
 A small program that is executed
when a computer boots up.
 E.g.-NYB, AntiExe, unashaned

10. 4) Multi-partite virus
 Infect boot records and programs files.
 Difficult to repair.
 Boot area & files must both be
cleaned of virus or re-infection will
occur.
 E.g.-one
half, emperor, anthrax, tequila

11. 5) Macro virus
 Most common type of virus.
 Infect data files like word, excel, power
presentation, access files.
 E.g.-W97m.melissa, WM.NiceDay &
W97M.groov

12. 6) Script virus
 Infect various script language such as
dos, java script & visual basic script.

13. 7) companion virus
 A virus which infects executable files
by creating a ‘companion’ file with the
same name but an .com extension.

14. Thank
you