Computer Virus

Introduction

Computer virus is a kind of program that destroys the functioning power of computer smoothly. Viruses have many purposes-some are designed to play annoying tricks, whereas others have destructive intent.

Symptoms of Virus

• Virus takes long time to load the program.
• It slows down the speed of computer.
• It shows unusual error message on the screen.
• It changes extension of files.
• Sometimes virus destroys the location of the files and files become inaccessible.
• It corrupts the system data.
• It reduces memory space of computer.

Prevention of Virus

• Load only software from original disks or CD's. Pirated or copied software is always a risk for a virus.
• Execute only programs of which you are familiar as to their origin. Programs sent by email should always be suspicious.
• Computer uploads and "system configuration" changes should always be performed by the person who is responsible for the computer.
• Password protection should be employed.
• check all shareware and free programs downloaded from on-line services with a virus checking program.
• Purchase  or download an anti-virus program that runs as you boot or work your computer. Up-date it frequently. There are free anti-virus programs available.

Types of Viruses

1. Trojan Horse: A Trojan Horse program has the appearance of having a useful and desired function. A Trojan Horse neither replicates nor copies itself, but causes damage or compromises the security of the computer. 


2. Worms: Worm is a program that makes and facilitates the distribution of copies of itself; e.g. from one disk drive to another, or by copying itself using email or another transport mechanism.


3.  Boot sector Virus: A virus which attaches itself to the first part of the hard disk it is read by the computer upon boot up. These are normally spread by floppy disks.


4. Macro Virus: Macro viruses are virues that use another applications macro programming language to distribute themselves. They infect documents such as: MS Word or MS Excel and are typically spread to other similar documents .


5. Memory resident Virus: Memory resident virus resides in a computer volatile memory (RAM). They are initiated from  a virus which runs on the computer and they stay in memory after its initiating program closes.


6. Polymorphic Virus: A Polymorphic Virus not only replicates itself by creating multiple file itself, but it also changes its digital signature every time it replicates.