4th June 2020



CLASS: Grade 5




Brief explanation

The term ‘computer virus’ was first formally defined by Fred Cohen in 1983. Computer viruses never occur naturally. They are always induced by people. Once created and released, their diffusion is not directly under human control. After entering a computer, a virus attaches itself to another program in such a way that execution of the host program triggers the action of the virus simultaneously. It can self-replicate, inserting itself onto other programs or files, infecting them in the process. Not all computer viruses are destructive though. However, most of them perform actions that are malicious in nature, such as destroying data. Some viruses wreak havoc as soon as their code is executed, while others lie dormant until a particular event (as programmed) gets initiated, that causes their code to run in the computer.


Computer Virus

A computer virus is a malicious program that self-replicates by copying itself to another program.

In other words, the computer virus spreads by itself into other executable codes or documents. The purpose of creating a computer virus is to infect vulnerable systems, gain admin control and steal user sensitive data. Hackers design computer viruses with malicious intent and prey on online users by tricking them.

One of the ideal methods by which viruses spread is through emails – opening the attachment in the email, visiting an infected website, clicking on an executable file, or viewing an infected advertisement can cause the virus to spread to your system. Besides that, infections also spread while connecting with already infected removable storage devices, such as USB drives.

It is quite easy and simple for the viruses to sneak into a computer by dodging the defense systems. A successful breach can cause serious issues for the user such as infecting other resources or system software, modifying or deleting key functions or applications and copy/delete or encrypt data.


How does a computer virus operate?

A computer virus operates in two ways. The first kind, as soon as it lands on a new computer, it begins to replicate. The second type plays dead until the trigger kick starts the malicious code. In other words, the infected program needs to run to be executed. Therefore, it is highly significant to stay shielded by installing a robust antivirus program.

Of late, the sophisticated computer virus comes with evasion capabilities that help in bypassing antivirus software and other advanced levels of defenses. The primary purpose can involve stealing passwords or data, logging keystrokes, corrupting files, and even taking control of the machine.


The History of Computer Virus

Robert Thomas, an engineer at BBN (Bolt Beranek and Newman) Technologies developed the first known computer virus in the year 1971. The first virus was christened as the “Creeper” virus, and the experimental program carried out by Thomas infected mainframes on ARPANET. The teletype message displayed on the screens read, “I’m the creeper: Catch me if you can.”

But the original wild computer virus, probably the first one to be tracked down in the history of computer viruses was “Elk Cloner.” The Elk Cloner infected Apple II operating systems through floppy disks. The message displayed on infected Apple Computers was a humorous one. The virus was developed by Richard Skrenta, a teenager in the year 1982. Even though the computer viruses were designed as a prank, it also enlightened how a malicious program could be installed in a computer’s memory and stop users from removing the program.

It was Fred Cohen, who coined the term “computer virus” and it was after year 1983. The term came into being when he attempted to write an academic paper titled “Computer Viruses – Theory and Experiments” detailing about the malicious programs in his work.




Types of Computer Viruses

A computer virus is one type of malware that inserts its virus code to multiply itself by altering the programs and applications. The computer gets infected through the replication of malicious code. Computer viruses come in different forms to infect the system in different ways. Some of the most common viruses are,

  1. Boot Sector Virus
  2. Direct Action Virus
  3. Resident Virus
  4. Multipartite Virus
  5. Polymorphic Virus
  6. Overwrite Virus

Boot Sector Virus – This type of virus infects the master boot record and it is challenging and a complex task to remove this virus and often requires the system to be formatted. Mostly it spreads through removable media.

Direct Action Virus – This is also called non-resident virus; it gets installed or stays hidden in the computer memory. It stays attached to the specific type of files that it infects. It does not affect the user experience and system’s performance.

Resident Virus – Unlike direct action viruses, resident viruses get installed on the computer. It is difficult to identify the virus and it is even difficult to remove a resident virus.

Multipartite Virus – This type of virus spreads through multiple ways. It infects both the boot sector and executable files at the same time.

Polymorphic Virus – These types of viruses  are difficult to identify with a traditional anti-virus programs. This is because the polymorphic viruses alters its signature pattern whenever it replicates.

Overwrite Virus – This type of virus deletes all the files that it infects. The only possible mechanism to remove it is to delete the infected files and the end-user has to lose all the contents in it. Identifying the overwrite virus is difficult as it spreads through emails.

THere are some simple rules you can follow to prevent your computer from being infected by viruses through email.

Do’s – The things you may do:
1.) Make sure your computer has updated anti-virus software running locally. Automatic updates are essential for effective virus protection.

2.) Disable message preview in your email client, especially on Windows platforms. Otherwise, malicious programs attached to incoming messages may execute automatically and infect your computer.
3.) Take caution when opening graphics and media attachments, as viruses can be disguised as such files.
4.) Maintain several independent email accounts. If a virus infects your only business email address, you’ll be in trouble.

5.) Also, keep backups of your most important email and files separately.


Don’ts  –  Things you may not do:
1.) Do not open an email attachment unless you were expecting it and know whom it is  from.
2.) Avoid downloading executable or documents from the internet, as these are often used to spread viruses.
3.) Never open files with a double file extension, e.g. filename.txt.vbs. This is a typical sign of a virus program.
4.) Do not send or forward any files that you haven’t virus-checked first.


How to Get Rid of Computer Virus

Never neglect to take action on a computer virus residing in your system. There are chances that you might end up losing important files, programs, and folders. In some cases, the virus damages the system hardware too. Thereby, it becomes mandatory to have an effective anti-virus software installed on your computer to steer clear of all such threats.


Signs of computer Virus Infection

It is vital for any computer user to be aware of these warning signs –

1.) Slower system performance
2.)  Pop-ups bombarding the screen
3.) Programs running on their own
4.) Files multiplying/duplicating on their own
5.) New files or programs in the computer
6.) Files, folders or programs getting deleted or corrupted
If you come across any of these above-mentioned signs, then there are chances that your computer is infected by a virus or malware. Not to delay, immediately stop all the commands and download an antivirus software. If you are unsure what to do, get the assistance of an authorized computer personnel.


  1. List 7 signs of computer virus infection.
  2. Explain one way you can get rid of computer virus.
  3. What is computer virus?
  4. List 8 types of computer virus.
  5. How does a computer virus operate?
  6. _________ developed the first computer virus.
  7. __________, ___________, ___________ and ___________ are the purposes for which computer viruses are developed.
  8. Write a short note on Polymorphic Virus.