Computer virus: types, symptoms, protection and removal

On this page, you will learn everything you need to know about the types, symptoms, protection, prevention, detection and removal of computer viruses.

This article is the result of several well-known sources.

What is a computer virus?

A computer virus is a type of malware (malicious software or code) that is designed to spread from computer to computer and perform harmful activities such as corrupting and disrupting systems or destroying data. (1)

Computer viruses can also copy (duplicate) themselves.

Computer virus types

A list of well-known computer virus types:

Computer virus symptoms (signs)

A few computer virus symptoms are:

Computer virus protection

The BEST protection against computer viruses is YOU.


You can have the best protection there is, but even the best antivirus software can fail to detect new malware (e.g., computerviruses, ransomware, spyware, etc.). (8)

Malware threats grow so fast, that antivirus programs take too long to catch up with malware (even the best free or paid ones). (9)

Therefore, the best protection is yourself.

If you do any of the following:

Then there's a good chance that your PC will get infected one day.

Antivirus software

It's recommended to always use an antivirus program on your PC – even when antivirus software can't protect your computer against all viruses.

It's better to have some protection than no protection at all.

You should only use one antivirus program on your computer.

The free antivirus programs I recommend are:

If you need more functions (e.g., multi-layer ransomware protection) and settings, then you can try a paid antivirus program.

Most antivirus companies offer the option to download and try their paid antivirus programs for free for 30 days.

The paid antivirus programs I recommend are:

Free second opinion virus scanners

It's also recommended to use second opinion virus scanners to get more complete detection coverage, because some programs may detect viruses that others might miss.

The free virus (malware) scanners I recommend are:

If you think that your PC has a virus (malware) infection, then you can also try the following free virus (malware) scanners:

You can use these virus (malware) scanners alongside your current antivirus software.

You can use these scanners to scan your PC periodically (e.g., once a week) or when you think your PC is infected with a virus or another type of malware.

Computer virus prevention tips

trick to install a computer virus on your computer

Computer virus detection and removal

I will show you how to detect and how to get rid of a computer virus for free.

But first:

The first thing you want to keep in mind when your PC is infected by a computer virus is whether or not you want to clean it. Because sometimes it may be a better idea to back up any data that you might have and reinstall Microsoft Windows or restore a system image backup that's 100% clean.


Well, if your antivirus (antimalware) software detected a computer virus or other malware, then you will never know for sure if that's the only piece of malware that has infected your system.

Malware can nestle itself deeper into your system and hide so that it can't be discovered by your security software and it can also open doors to other malware.


You also may end up with a damaged Windows installation.

Considering time and effort, sometimes it's better to wipe everything and start all over again. But, if you wanted to do that, you probably wouldn't be reading this article, so, follow the steps below.

With the following steps, I assume that you have access to your system or at least can boot Windows into “Safe Mode with Networking”.


If you cannot access your computer then I recommend Kaspersky Rescue Disk (located in the “Free Tools” section).

Once you have the ISO file you can install it on a USB flash drive with the help of a free tool called Rufus and then you can boot from the USB drive and use the rescue disk.

Let's continue with the next step.

Step 1: Find out if your files are affected by Ransomware

If you cannot open some files on your computer or you see files with missing or weird file extensions (e.g., .cry, .crypto, .locked, .kraken, etc.), your system is probably infected by Ransomware.

If your system is infected by Ransomware, the first thing you should do is to check if your files can be decrypted.

But to do this, you first need to find out which Ransomware has infected your PC.

To find out which Ransomware has infected your PC, look at the ransom note, or look at any messages on the screen or look at the encrypted files and the extension they have.

If you cannot find out which Ransomware infected your PC you can visit ID Ransomware by MalwareHunterTeam and upload the ransom note or an encrypted file.

You can also visit a cybersecurity forum like BleepingComputer.

On this forum, you can find a lot of malware analysts that you can talk to.

You can post something in the forums and upload one of your encrypted files.

They might be able to tell you whether or not you can decrypt your files.

You can also download the Bitdefender Ransomware Recognition Tool to find out which ransomware has encrypted your data and then get the appropriate decryption tool if it exists.

You can visit or the free ransomware decryptors page on and check if they have a decryptor tool for the ransomware that infected your PC.

Step 2: Make a backup of your files

If your files were not affected by ransomware or you were able to decrypt your files, then you should make a backup of your files.

You can use a free backup program like AOMEI Backupper Standard or copy your files to a USB flash drive or external hard drive.

Step 3: Disable startup programs in Windows

1. Open Windows Task Manager.

Three ways to open Task Manager:

2. Click on the Startup tab.

Note: if you don't see the Startup tab then click on More details located at the bottom left of the Taskmanager window.

3. Disable everything that you see here, including your antivirus software.

To do this, right-click on the program and then click on Disable.

Disable startup programs in Windows

Step 4: Disable services in Windows

1. Open Windows System Configuration.

Three ways to open System Configuration:

2. Click on the Services tab.

3. Check (select) the Hide all Microsoft services option located below the list.

4. Click on the Disable all button.

Disable services in Windows

5. Click on the Apply button.

6. Click on OK.

7. Click on Restart to restart your computer.

Step 5: Scan your computer with malware scanners

You can use malware scanners to scan your computer for malware, and hopefully, also remove malware.

Malware scanners can run alongside your antivirus without any problems.

The free malware scanners I recommend are:

These malware scanners work pretty much the same way. You download them, open them, and then click a button to start a scan.

Make sure you double-check the scan results, in case they found something harmless, and uncheck everything that's harmless before you click to continue the removal process.

Hopefully, you learned enough about computer viruses to keep your PC clean and secure. If you want to learn more about computer and Internet security (cybersecurity), then you can visit .

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Windows 10 security tips and is Windows Defender good enough?


Wikipedia: Computer virus

Webopedia: Memory resident virus

Webopedia: Overwriting virus

SpamLaws: Direct action virus

Kaspersky: Boot sector virus

Webopedia: Cluster virus

TechTarget: Macro virus

LastLineLabs: Antivirus isn't dead, it just can't keep up

GCN: Is antivirus now useless?

YouTube: How to clean an infected computer