What are Computer Viruses and What does it do?


What Are Computer Viruses

Computer viruses are a real threat to anyone that uses computers.

Computer viruses are essentially programs or pieces of code designed to alter your computer in some way.

Normally, this alteration is unwanted; the virus will delete files on your computer, steal personal information like credit card numbers and passwords, or even gain access to sensitive material like classified government documents.

Computer viruses can also be less malicious; sometimes they’re simply time-consuming annoyances that make it impossible for you to do anything with your computer except restart it (this type of virus is called a “boot sector” virus).

Computer viruses were first seen in the 1980s at MIT when two programmers created what was known as the “Creeper Virus.” Little did they know that it was the beginning of a new era in technology.

Resident and Non-Resident Viruses

Computer viruses can be either “resident” or “non-resident.” This refers to how the virus sticks itself into your computer’s memory and stays there. A non-resident virus will only activate when you open an infected file, while a resident virus attaches itself to your computer and runs every time you turn it on.

Resident viruses were rare until 1987 when Brain, one of the most famous viruses in history, was created by two brothers from Pakistan. It is said that it caused nearly $5 billion dollars’ worth of damage and 5 million infections.

Today we have better protection against computer viruses than we did 30 years ago; however, it’s still important to properly defend yourself if you know what we’re up against.

It is estimated that less than 1% of all computers are infected by viruses, however these viruses are not harmful and are mostly dormant in the background. The riskiest viruses are the ones that actually have a harmful effect, these viruses can remove files from your computer, or you may even have to reformat your entire hard drive.


What does a computer virus do?

If you’re concerned about viruses, here’s what they do:


First of all, computer viruses are bits of code that attach themselves to other files and spread as those files travel from one computer to another. Viruses come into your computer as an attachment or embedded within a website link and can be opened by unsuspecting users (such as yourself). Once inside they go through the process named “spreading” by programmers, meaning they will try to infect everything possible on your system with their own self-replicating code or program.

For example, if a virus is an email message with an infected picture attached to it, when you open the email and download the picture Windows will also run executable code automatically without your knowledge and install the virus in the background.

In this case, the virus will infect your email program with a small file extension called a “CODE” or “EXE”. This code is a small set of triggers + a payload that can do anything from changing system files to stealing private information and sending it back to the creator’s servers.

Once installed the virus may install other programs automatically without you knowing it. For example, one of the most common viruses on Windows operating systems is “Zeus Virus”, which scans all active threads in applications such as browsers or chat software for credit card numbers and passwords. Then sends them back to its main server so anyone on their way can steal your identity and drain funds from your bank account over time until nothing is left.

Password Encrypt Your Files

Another thing that viruses can do is encrypt your data files. The virus will take all of your important files, which are usually pictures, documents or other personal files and then encrypt them so that you can’t use them until you pay for a key to decrypt the data to get your original file back. However, this is just one option viruses must make money. These are called as Ransomwares.


Another thing that viruses do is spam everyone on the computer it has infected asking for money. Even though most computer users know this isn’t real it still annoys almost every user because there are always calls for help or calls for attention about family problems or sick children asking people to send money right away to save someone’s life.

Corrupt System Files

Another thing that viruses do is corrupt system files and restore points so that they cannot be used. Viruses can also disable system services and applications so that they cannot run properly. This can also

Vulnerable components on your computer are especially at risk, like *.sdb files (page file) or the *.exe files in the Windows folder. These both contain information about what you had running on your machine when it was infected by malware, which is why some people say that virus removal is sometimes more difficult than creating viruses.

Access to hackers

The usual consequence of a virus is that the person who created it gains access to your computer, and can use it for whatever they want, which is usually to send spam email or commit other types of identity theft. They might also just lock you out of your own computer by using some advanced form of ransomware, so please keep yourself safe by having antivirus software installed on all devices connected to the internet.


Send data back to its creator

The last thing a virus does is send data from your computer back to the person who created it. This takes place over the Internet for example through email attachments; but some viruses copy themselves across other types of removable media like USB sticks. However, some very dangerous viruses do not spread themselves over such removable medias or internet connections.


If a virus makes it past the first line of defence and infects a computer, there is no known way yet to delete it off your computer without deleting other files as well. The only way to get rid of this type of virus is to re-install windows again (i.e., reinstall all programs and registry entries) or use an antivirus program that has been updated with the latest definitions for that specific virus. Unfortunately, this is something that you may not be able to do yourself and would need to contact us for repairs.

Interesting read: WannaCry Ransomware – All You Need to Know

I am a computer engineer holding a bachelor's degree in Computer Science, complemented by a Master's in Business Administration from University of Strathclyde, Scotland. I currently work as a Senior IT Consultant in Melbourne, Australia. With over 15 years of...