What is Computer Virus? || Types of Viruses || Antivirus definition

What is a Computer Virus: Computer systems are vulnerable to many kinds of threats that can cause various types of damages, resulting in significant data loss. 

These threats can be in the form of computer viruses, worms, and Trojan horses. 

Viruses that attack a computer are actually programs that have been deliberately written by bad guys called Virus Programmers. 

The virus copies itself to your Computer memory and infects disk(s) attached to the computer. Virus Programmers are like crackers who breach the computer system, in order to steal information or cause harm to computer systems. They program dangerous viruses to get access to computer systems.

What a Computer virus does? 

Computer viruses disrupt the system by deleting files in the system, formatting the hard disk, overwriting the system BIOS, or completely disabling the computer. The various harmful effects of computer viruses are listed here :

• Increasing the size of files by attaching themselves to the files.
• Corrupting the data or program files. 
• Formatting the hard disk, thus destroying data.
• Slowing down the system by occupying most of the memory space. 
•  Renaming all files and folders with the same name. 
• Infecting disks by corrupting boot sectors. The boot sector of the hard disk contains special programs that are required to start up the computer system.

How a Computer virus spreads? 

Viruses usually enter the computer system through external sources like infected Floppy Disks, Compact disc, Pen Drive, and the Internet. Once a virus enters a computer system, it spreads to other programs also. Following are the various ways in which it spreads : 

• Viruses can enter the system where the system is booted with an infected disc, i.e., CDs, DVDs, and   Pen drives.
• Some viruses infect the system when a file is copied from an infected disc, i.e., CDs, DVDs, and Pen drives.
• Viruses can also be passed from one computer to another when data or programs are accessed on a network or a file is downloaded from the Internet. 
• The more a system comes in contact with the Internet or with an infected CD disc, the higher is the risk of it being infected with a virus.

Types of Viruses

A virus is a piece of code that is embedded in a legitimate program. Viruses are designed to infect self-replicating and other programs. They can cause system crashes by modifying or deleting files due to system crashes or program errors. 

When a virus dropper (usually a Trojan horse) reaches the target machine, the virus enters the system.

• File Virus
• Boot sector Virus 
• Macro Virus
• Source code Virus
• Polymorphic Virus
• Encrypted Virus 
• Stealth Virus
• Tunneling Virus
• Multipartite Virus 
• Armored Virus

Preventing virus Infection

The following is a list of the do and don'ts for preventing virus infections in a system : 

Never insert an unknown disk into your computer unless you make sure it is virus-free.

• Always scan the disc or pen drive with an antivirus application be using them.

• Do not use illegal software, it may contain a virus.

• Always keep the Auto-Protect, Internet-worm Protection, and E-ma scanning features of anti-virus software to prevent downloading of infected files. 

• Always check if your computer demonstrates any strange behavior.

1. slowing down the speed of your Computer system

2. disappearance of files. 

3. taking longer time in the loading of programs.

4. decrease in the free space available on the disk.

5. recent creation dates on old program files.

Antivirus Software 

Anti-virus software is an application program that is designed to detect and remove viruses, worms and Trojan horses from the computer system. An anti-virus software looks for these computer threats in all the files and folders of the computer system. 

If looks for changes and activities in the system that are typical in case of a virus attack.

Scanners that are built within the anti-virus software look for particular types of codes within programs. If a virus is detected, the anti-virus tries to remove it from the system. The most popular anti-virus software are :

1. Norton Anti-virus Software 
2. McAfee Virus Scan Software 
3. AVG Anti-virus Software
4. E-Scan Anti-virus Software 
5. F-Secure Anti-virus Software

A Computer virus is a program that is designed to perform desired and malicious actions by replicating and attaching itself to other programs. A Computer Virus cannot infect computer Hardware such as keyboards, monitors, and so on. It infects only the software. 

Viruses usually enter the computer system through external sources like infected Floppy Disks, Compact Discs, Pen drives, and the Internet. 

Anti-virus software is an application program that is designed to detect and remove viruses, worms, and Trojan horses from the computer system.