Guide to all you need to know about computer viruses

Last update May 30, 2023 at 10:57 am

A short guide to demystifying computer viruses. After reading you will sleep less stupid !!

In life, there are two types of people. Those who do good and those who harm others. While in reality a person can be both good and bad depending on the circumstances, in the digital world the distinction is more visible.

There are programs that make our lives easier and those that disturb us. These will constitute what is often called a virus. In this article we present to you as a guide everything you need to know about computer viruses.

Guide to all you need to know about computer viruses

Guide to knowing everything about computer viruses in 2021

A virus is a computer program able to duplicate itself, to settle without the knowledge of its victim and to perform the tasks for which it is programmed. Its behavior is similar to biological viruses.

Originally viruses were just part of a computer game concept from developers called Core War. Today computer viruses are in class softwares malicious called malware. 

Contrary to popular belief, viruses do not come from dust, nor from lack of maintenance of the machine and even less from used computer equipment. Viruses are programs created by humans like you and me. There are 2 main categories of viruses: you have surely heard of malware and spyware.

I / Malware and spyware

 Malware or malicious software: are software intended to disrupt, modify or destroy all or part of the elements essential to the proper functioning of the computer.

As soon as this software has the ability to multiply, it can be classified as a computer virus.

Spyware or spyware is malicious software whose purpose is often to collect information from its victim and transfer it to its programmer.

For example they can copy the passwords of their victim and send it to whoever created it. It is widely used in computer hacking

All computer viruses are malware, but malware is not necessarily a virus. The difference is that one is able to duplicate itself very quickly while the other (malware) may not have this ability.

To get rid of it, you have to use anti-malware instead of antivirus. For more information, I invite you to read the following post:

II / Why do we create computer viruses (and why so much hatred)?

There are several motivations behind the creation of malware. The reasons that come up often are:

  • Entertainment: to prank or to perform a specific task.
  • To hack : hackers use it to create a loophole in the system through the backdoor strategy. This hacking strategy allows its user to leave a virus in the victim's system. This virus secretly creates a loophole in order to hack into the system more easily next time.
  • Spying and collecting information from others.
  • Have total control on the machine and use it to attack other computers. This is a strategy often used by hackers to cover their fingerprints and make themselves 'invisible'.

Computer viruses are also used in war and politics to steal important information.

With their mode of operation, they can be organized into several types.

III/ The different types of computer viruses according to their mode of operation/attack?

Viruses are categorized according to their mode of operation. There are at least 7 types of viruses:

1 / Macros viruses

These are viruses programmed only to attack the Microsoft Office suite. Our virus is programmed in vba to modify the code of the macros of the suite and cause them to malfunction.

According to wikipedia, this virus is the easiest to program. So be careful when you enable macros in Microsoft Excel, it's not for nothing that they are disabled by default.

2 / Viruses-worms

These are computer viruses that embed themselves in programs and multiply ad infinitum in internet networks.

This type of virus generally does not destroy machines (at least initially) but reduces the performance of computers and infected machines.

3 / Boot viruses or boot sectors

This type of computer virus has an insatiable preference for hard drives, usb keys or other storage media rather than digital files. They replace every memory block in the computer with whatever. The worst thing is that this type of virus is difficult to detect and destroy.

Why ? Because a simple formatting of the support will not make it leave and the difficulty worsens if this virus is in the MBR of your machine.

For your information, the MBR (master boot record) is system software that allows you to launch your operating system (microsoft, linux or OSX) when the computer starts up.

4 / Logic bombs 

 Ce are viruses that are triggered following a specific event. For example on Valentine's Day, almost everyone who turns on their pc sees this text “you are going to hate me in 3 seconds” displayed. After 3 seconds your pc turns off. It really happened.

5 / Trojans

These are malware designed to create vulnerabilities in computer systems. Most often it is to allow their designer to break into the infected system to take control of it.

6 / Hoaxes (hoaxes)

Hoaxes or hoaxes can be announcements received by email that encourage people to share information with their relatives.

For example, we can announce the appearance of a new destructive virus or the possibility of winning a mobile phone for free, accompanied by a notes specifying to forward the news to all his relatives.

The purpose of this process is to clog the networks as well as disinformation.

Yes a virus can spread Fake News.

7 / ransomware

It is a malicious software that blocks access to your machine's system and demands a ransom from you in order to unblock it.

Generally it is not complex for a connoisseur to unlock his computer without paying. However, a type of ransomware called cryptovirology encrypts the victim's files using a secret key without which it is impossible to decrypt the files.

This type of ransomware offers to provide file decryption key in exchange for some amount of money. More often than not, bitcoin is widely used.

 8 / Other types of computer virus

 Other types of viruses are adware or adware. Like the definition of its name, this virus bombards you with advertisements. It's now more common in smartphones than PCs.

Most often, we see in our phones ads appearing outside of applications and it is difficult to find the source of this one.

We have finished talking about the different categories and types of viruses, it would be interesting to know the most famous viruses that have been talked about. Don't forget that a virus can be of several types because they use several modes of operation mentioned above.

IV / The most famous and well-known viruses

We know that computer viruses are harmful to our machines. But we don't all realize how dangerous they are. To understand, nothing beats examples of the most famous viruses and their operating strategy.

1 / Sircam

Sircam is both a logic bomb and see which is spread by Microsoft Outlook e-mails. The computer virus attacks by choosing a document from your “my documents” folder. he then sends an e-mail having for subject the name of the document which he attacked and the copy of the virus in attachment.

2 / Stuxnet

This is a war virus, discovered in 2010 by a computer security company VirusBlokAda, this worm has the ability to spy and reprogram industrial systems. As a result, out of 45000 systems infected with this around 30000 were discovered in Iran and the other 15000 distributed in France, Germany, India and Indonesia.

3/ “I love you”

 A virus that has broken many hearts ... this computer worm is spread by email and email attaching a named attachment "LOVE-LETTER-FOR-YOU.TXT.vbs ”, when the user clicks on this script it runs by modifying the registry base to make its execution time infinite. It then multiplies in several windows system folders to modify the auto-launch register base in order to run each time windows starts. Once the operation "Love" successfully completed, this computer virus modifies the home page of the internet browser to download the trojan horse WIN-BUGSFIX.


This Trojan is downloaded by “I love you” virus. The latter copies Your password then sends it by email to its designer. It will then create a web file responsible for executing the scripts containing the viruses”I love you” previously duplicated in the system folders to then send it to the victim's contacts. This computer virus aims to collect passwords and then send the virus "I love you" contact with the victim. And the process resumes with each of them. Result: 350000 computers infected with the “i love you” virus in 10 minutes. The verses Bill Clinton, Ben Laden, Anna Kournikova are the clones of “I love you”.


It is a worm and ransomware type computer virus. He infects his victim's machine via the internet and gives him a one hour countdown to pay the ransom. Spend this time, the virus exponentially deletes victim's files hourly. If in an hour it deletes a file, in two hours it will delete 2-3 more in the machine until nothing is left.


This ransonware only attacks businesses. it encrypts companies' data and then asks them for a large sum of money in return.


A spy-type virus discovered in 2014 by two giants, creators of computer antivirus, Kaspersky Lab and Symantec (creator of Norton antivirus). It is used as a cyber espionage platform against both private and public organizations. It allows you to listen to telephone conversations, read emails, collect information up to mot de passe in real time.

According to information revealed by Edward Snowden, this virus is created by the NSA in collaboration with the British spy service, GCHQ.


A computer virus that made a lot of people cry in 2017 on windows. It is of the worm and ransomware type. It encrypts its victim's data making it impossible to recover it and demands a ransom in bitcoin. Which makes the transaction impossible to trace.

Guide to knowing everything about computer viruses in 2021