Introduction to Computers: Computer Virus

computer virus



In this chapter, we will learn what the computer virus or viruses is/are, their source and effects, ways of avoiding their spread and also ways of removing viruses on a computer.


In this module, we will cover the following sub-topics
  • Computer virus
  • Worms
  • Antivirus software
 Computer virus

A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. The original virus may modify the copies, or the copies may modify themselves.


Virus spread

A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or the Internet, or by carrying it on a removable medium such as a floppy disk, CD, or USB drive.

Meanwhile, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer. Viruses are sometimes confused with computer worms and Trojan horses.


A worm can spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a file that appears harmless. Worms and Trojans may cause harm to a computer system’s hosted data, functional performance, or networking throughout when executed. In general, a worm does not actually harm either the system’s hardware or software, while at least in theory; a Trojan’s payload may be capable of almost any type of harm if executed. Some can’t be seen when the program is not running, but as soon as the infected code is run, the Trojan horse kicks in. That is why it is so hard for people to find viruses and other malware themselves and why they have to use spyware programs and registry processors.


Some malware is programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Other malware programs are not designed to do any damage, but simply replicate themselves and perhaps make their presence known by presenting text, video, or audio messages. Even these less sinister malware programs can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes

Antivirus software

Antivirus software is computer programs that attempt to identify, neutralize or eliminate malicious software.

Antivirus is so named because the earliest examples were designed exclusively to combat computer viruses; however, most modern antivirus software is now designed to combat a wide range of threats, including worms, Trojan horses and other malware. Antivirus software typically uses two different approaches to accomplish this:

Examining (scanning) files to look for known viruses matching definitions in a virus dictionary, and identifying suspicious behavior from any computer program which might indicate infection.

The second approach is called a heuristic analysis. Such analysis may include data captures, port monitoring, and other methods. Most commercial antivirus software uses both of these approaches, with an emphasis on the virus dictionary approach. Some people claim that a Firewall program performs the functions of an Anti-Virus, however, they are mistaken.

 Review questions

Explain a computer virus and explain how computer viruses are propagated

What do you understand by the term protocol? Give two examples of protocols


In this lesson, you have learned what the computer viruses are, the way they spread, ways you can prevent your computer from viruses and usage of antiviruses.

Read Also: Computer network