Computer Virus - SEE Computer Science - Chapter 4

Chapter -4

Computer Virus

1.      Computer virus
Computer virus is a type of computer program which is written by the programmer with the intent of destroying or damaging the data and programs residing in the computer system. E.g. C-Brain, Frodo, Disk Killer, I Love You etc

The purpose of creating computer virus are:

a)      To stop computer piracy

b)     To entertain user by displaying interesting message and pictures

c)      To destroy data, information and files

d)     To expose the programmers ability

e)      To earn money

2.      Common characteristics of computer virus

a)      Destroy data, information, files or programs of a file.

b)     Steal important data and information.

c)      Load and run unwanted applications.

d)     Display the unnecessary messages or pictures.

e)      Degrade overall performance of the computer system.

3.      Spreading computer virus

a)      Sharing infected internal portable disk like floppy disk, pen drive, CDs, etc.

b)     Opening a virus infected email, messages and attached files.

c)      Downloading files and programs form the websites which are not secure.

d)     Exchanging data and information over a network

4.      Symptoms of computer virus

a)      Program takes long time to load.

b)     The floppy disk or hard disk is suddenly accessed without a logical reason.

c)      Increased use of disk space and growth in file size.

d)     Corrupting the system data.

e)      Renaming files with different names.

5.      Effects of computer virus

a)      Virus can change the contents of file, and codes of program.

b)     Degrade the overall performance of computer system.

c)      Change in size of file by adding or removing text accordingly.

6.      Preventive ways to protect computer system form virus

a)      Write protect your floppy disks when using them on other computers.

b)     Scan the mail or unknown files of internet before opening in your computers.

c)      Use a good antivirus program to scan floppy disk, CD, etc. before copying.

d)     Don’t install pirated software, especially computer games.

e)      Don’t interchange the internal disk among the computers.

7.      Types of viruses

a)      Boot sector virus

b)     File infector virus

c)      Multipartite virus

d)     Stealth virus

e)      Macro virus

8.      Antivirus software
Antivirus software is software designed to detect and remove virus from computer system o ensure virus free environment. E.g. Kaspersky, NAV, McAfee, NOD 32 etc.

9.      Boot sector virus
Ans: The virus which destroys or infects the boot sector of the disk where master boot record is stored is called boot sector virus. The boot sector virus modifies the Master Boot Record (MBR) that prevents the computer system from being able to boot or start up the computer from system disk. MBR is a small program which is responsible for booting computer system.

10.   Program or file virus
The virus that infects the executable program file having extension .exe, .bin, .sys, .com, etc. is called program virus.

11.   Stealth virus
The virus that infects the program files and boot records which rarely gives the information about its presence is called stealth virus.

12.   Multipartite virus
Ans: The virus which infects both application program and boot sector of a disk is called multipartite virus.

13.   Macro virus
The virus that infects the software document or template created using word processing or spread sheet software is called macro virus.

14.   Computer worm
A computer worm is a malicious program that does not hide in other files but operates entirely on its own.

15.   Trojan horse
Trojan horse is a destructive program that disguises as a game or a utility or an application program, which pretends to be something interesting and harmless.