What is a Computer Virus?

As the name implies, a computer virus is a type of malevolent software whose main objective is to align itself into a healthy host application code. This is for the sole purpose of self-replication. Cyber attackers use viruses to take control or simply damage a computer.

The word ‘virus’ comes from the fact that this type of malware infects its target in a similar manner to a biological virus such as the flu or HIV. A computer virus requires a host otherwise it cannot self-replicate. It typically sneaks into the unsuspecting host organism through the code snippet of an application. What triggers the virus into action is running of the application.

With that said, most people tend to use the words malware and virus interchangeable. But a virus is actually a kind of malware. There are other types of malware that follow different mechanisms of action, such as Trojans. A Trojan virus hides inside the computer’s system. They’re so stealthy that it’s easy for anyone to just click on them thinking they’re legit programs.

A worm can pretty much spread without being dependent on another application. What is a computer virus? The main distinguishing factor of a virus is that it needs a host application or program in order to proliferate and actually operate.

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What Do These Viruses Do?

What is a computer virus? To explain, let’s say one of the apps in your computer gets a virus infection. How does a computer virus work? Well, it usually follows a relatively obvious mechanism of action. It starts when the infected application takes some type of action. This is typically set off by the user. Once this happens, the code within the virus goes into the CPU memory first. This is before the actual, legitimate code.

Then the virus starts spreading all over the place. It infects a number of other applications and spreads its malicious code all over the place. With a resident virus, this happens whenever you open a new program. On the other hand, a non-resident virus can actually do its dirty work even on stagnant programs.

Boot sector viruses, on the other hand, infect the computer’s boot sector which is located in the system disk. This is to ensure that the virus gets triggered from the moment you switch on your computer. That way, the virus will proliferate prior to you even loading the operating system.

How Do They Spread?

What is a computer virus and how do they spread, you ask? Back in the day, the only way to get a virus was to insert an infected floppy disk into your computer. That’s pretty much how they spread. This was the case with the infamous SCA virus which spread through pirated software disks. Through this method, the SCA virus managed to infect up to 40% Amiga users.

Nowadays, the most common way for viruses to spread is through the Internet, specifically apps that people share from one device to another. Keep in mind that a majority of viruses carry a logic bomb. This is a code that executes the payload at under specific conditions. This is part of what makes this type of virus so difficult to trace because it can spread rapidly without anyone being the wiser.

Cybercriminals are getting really creative with the methods they use to spread these viruses. You could receive an infected application via email or download it from a compromised app store. The one thing virus infections have in common is the fact that they require a host application. This is how they piggyback from one device to another.

Most Common Types of Computer Viruses

There are many different categories of computer viruses out there, as cybercriminals are always coming up with new ways to steal people’s data, identity, and money. Through this article, we’ve already touched on what the most common types are, including web scripting viruses, boot sector viruses, as well as resident and non-resident viruses.

Here are a few important types to be aware of:

  • A micro virus typically piggybacks onto a macro application. This is hidden in a PDF or Microsoft Office file. A lot of people don’t really consider these files to be dangerous but they can harbor malicious code which activates as soon as you open the file.
  • A polymorphic virus is even more dangerous because it has the ability to alter its source code in order to hide from antivirus software.


These virus categories are predicated on the behavior of the virus itself. Hence, certain viruses can actually tick more than one box in these categories.

You can use Defencebyte to get rid of any type of virus on your devices. The software will always notify you every time you visit an unsafe website or download a virus.

Did this article help you find what is a computer virus? Let us know in the comments below.


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