Introduction To Computer Viruses

The Oxford English dictionary defines a virus, as a small living thing that causes infectious illnesses. For instance, HIV/AIDs Virus.

However, in computers, a virus is an undesired piece of code, that infects a system with the intention of making it malfunction, or not even function at all. Viruses cannot just arise spontaneously. It is man-made.

In the field of computers, VIRUS stands for Vital Information Resource Under Siege.

What are Computer Viruses?

Computer viruses are small software programs, that are designed to spread, from one computer to another, and to interfere with computer operation.

A computer virus might corrupt or delete data on your computer, use your email program to spread itself to other computers, or even erase everything on your hard disk.

It is important to note that virus falls under the category of malware. Malware is short for “malicious software” and is used as a single term to refer to a virus, spyware, worm, etc. A virus is a specific type of malware and its definition is limited only to programs or code that self-replicates or copies itself in order to spread to other devices or areas of the network.

Computer viruses are often spread by attachments in email messages or instant messaging messages. That is why it is essential, that you never open email attachments, unless you know who it is from, and you are expecting it.

Computer viruses also spread through downloads on the Internet. Most computer viruses have irritating damage, although there are some that are not all that harmful. They can be transferred from computer to computer, through Removable disks.

Examples are the typo virus which affects keystrokes, the Italian virus which produces a single character bouncing ball across the screen, the Dbase virus corrupts data to an unimaginable degree, La-Avenger virus affects files as they are opened and closed. Trojan viruses are a type of malware that invade your computer disguised as real, operational programs.

Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of the personal computer, many users regularly exchanged information and programs on floppies.

Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user wants to boot the computer from the disk, usually inadvertently. Personal computers, of the era, would attempt to boot first, from a floppy, if one had been left in the drive.

Until floppy disks fell out of use, this was the most successful infection strategy, and boot sector viruses were the most common category of computer viruses. Traditional computer viruses emerged in the 1980s, driven by the spread of personal computers, and the resultant increase in modem use and software sharing.

Types of Computer Viruses:

There are two major types of Computer Viruses;

1. Boot Sector virus.

2. Executable file virus.

We will discuss both in the coming topics.