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.
4.
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.