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How Does a Computer virus infect computers?

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Only by executing the computer virus program, your device may get infected. It must be run directly by the user or indirectly by attaching itself to other programs, documents, or files. A virus program may also hide in the code that is run automatically when you interact with the system or opening different files.

Mine and my family’s online safety is a priority to me, that’s why I am using Bitdefender Total Security Anti Virus which in my mind is the best Anti Virus software currently available.

I will strongly recommend checking the Bitdefender site for the latest offers.

What is a Computer Virus?

An American Computer Scientist, Fred Cohen known for his pioneering work on computer viruses, formulated the computer virus definition in 1984.

We define a computer ‘virus’ as a program that can ‘infect’ other programs by modifying them to include a possibly evolved copy of itself. With the infection property, a virus can spread throughout a computer system or network using the authorizations of every user using it to infect their programs. Every program that gets infected may also act as a virus, and thus, the infection grows.

F.B Cohen: Computer Viruses – Theory and Experiments.

Majority of viruses targets Windows users, not because the system is vulnerable and easier to penetrate but because there is simply more computers with Windows operating system around the world than macOS.

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As of 2020 approximately 80% of computers worldwide are running Windows and only 18% various versions of macOS.

Targeting a larger operating system market share, the computer virus authors simply increases the chances of success and a wider infection spread.

According to Malwarebytes, computer viruses are a thing of the past. Although they still exist and are a threat, cybercriminals shifted their tactics and started developing other malware types for financial gains.

Cybercriminals aren’t creating new viruses. Instead, they are focusing their efforts on more sophisticated and lucrative threats. When people talk about “getting a virus” on their computer, they usually mean some form of malware—often a computer worm.

Malwarebytes: Computer Virus – virus protection and removal.

What are the primary sources of computer virus infection?

Downloading unknown software.

Downloading and using unknown software carries the risk of computer virus infection. The software intentionally written to infect and spread the virus will often imitate other popular programs.

On mobile devices, you can infect your phone or tablet with malware by installing apps from unknown sources, so make sure to download the apps from the official AppStore whether this is on Android or iOS.

You may also like: If Free Anti Virus Good Enough, or should I buy One?

Make sure your computer software comes from a reputable source before downloading. Avoid downloading software from forum links, links in emails or other unknown websites. If you like to download the software mentioned on the forum, google it and download directly from the software vendor website.

Downloading pirated software.

The pirated software often contains a Crack which is a small program that generates license key or modifies the software files to circumvent the security measures that make the software unusable without the genuine license.

The Crack program may also do much more and infect your computer with a virus, adware or ransomware without you even knowing as it often requires administrative privileges to run in the first place.

Even visiting the websites which offer pirated software can be dangerous. They are usually littered with spammy ads or will try to redirect you to more danger sites, trying to infect your computer with malware.

Stay away from pirated software, and if you can’t afford the genuine version, try to find an open-source alternative.

Once again, the example below shows how my Bitdefender Total Security warned me about visiting and downloading a potentially harmful copy of pirated software or even visiting the page.

A warning message on the website generated by Bitdefender Total Security after attempting to download malicious file.
An attempt to download malicious file was blocked by Bitdefender Total Security software.

Opening unknown email attachments.

Opening email attachments is one of the most common sources of computer virus infection. The virus can imitate other files like images, movie files and so on with email titles often formatted to imply urgency, making the user more likely to open the attachment.

Don’t be fooled by emails sent from someone you know. Computer viruses often use infected devices to spread itself via email.

If the family member or a friend opened the attachment with a virus and infected their machine, there is a big chance that the virus will now try to spread by sending itself via email to any person in the contact list.

Image showing an example of a spam or malicious email.
Example of a spam or malicious email.

Visiting malicious websites.

Keep an eye on the websites you are about to visit or links you click.

Have you ever seen clickbait ads?

For example, where you have a minute to collect the prize or be gone forever?
Or the one where you have a new message, and you should click it to read it?

Don’t click these links!

Of course, not all clickbait ads are malicious, but nothing good usually comes from clicking them, so stay away.

Removable Storage.

With an uprise of cloud storage and high-speed internet, removable media like your flash drive are being used less and less for data transfer. That doesn’t mean that you can’t infect your computer by copying an infected file or program and running it on your machine.

Make sure to always scan your flash drive or external hard drive with Anti-Virus software before opening any files or programs stored on it.

I have been using Bitdefender Total Security Flash Drive Autoscan option, which, as the name suggests, automatically scans any devices capable of storing data I’ll connect to my computer.

Image showing the results of scanning removable storage by Bitdefender Anti-Virus software.
Bitdefender Total Security – scanning removable storage.

Is Malware a Computer Virus?

Any type of malicious software designed to cause damage to computers, networks, or servers is called Malware, including Computer Viruses. However, the Computer Virus is a special type of Malware which is capable of self-replicating and spreading.

There are numerous different types of Malware, and Computer Virus is just one of them.

Common types of Malware.

Adware.

Adware programs have been designed to deliver an unwanted advertisement to the infected host computers. They may take the form of a pop-up message in the system urging you to click the link or direct ads on the webpage.

An Adware was highlighted in Malwarebytes 2020 State of Malware annual report as the number one threat category in 2019, affecting both business and consumers alike.

The prevailing thinking is that Mac users are typically less affected by malware or computer virus infections.

Well, think twice.

According to Malwarebytes report, approximately 24 million Adware detections were made on Windows and 30 million on Mac.

Ironically, I had become a victim of an Adware recently when I researched this article’s topic. I have visited a malicious site by accident and clicked one of the links without paying attention.

The image below is the Windows pop-up message which imitated the Windows warning message about potential virus infection. However, you can see the link above the More button, which once clicked it redirected to the dating site.

Unfortunately, this time my Anti-Virus software was unable to detect the threat, and I had to download Malwarebytes software to remove it which it did successfully.

Screenshot of the Adware pop-up message in Windows 10  with a embedded malicious link.
An example of Adware pop-up message in Windows 10 with malicious link.

Spyware.

Spyware is what the name suggests. It is malicious software designed to spy on you when you interact with a computer or a mobile phone. It records your browsing history, keystrokes, payment information or your login credentials.

The data collected is then sold, usually to cybercriminals who will then try to use that data to access your accounts or even still your identity.

Ransomware.

Ransomware may completely take over your machine. It will prevent you from accessing the system until you pay the ransom. The email attachments are typically the primary source of infection following by general spam.

Ransomware is one of the most dangerous types of malware, in my opinion. It may encrypt your entire data stored on the computer in exchange for ransom, typically in Bitcoins.

It is crucial that you backup your data regularly to avoid losing it when infected with ransomware.

If infected, don’t pay the ransom as you never know if you get your data back. Paying the ransom will also encourage the cybercriminals to continue their efforts.

Unfortunately, once infected, it is not much you can do to get your data back once encrypted by the malware. In most cases, the best option is to disconnect the computer from the internet or network, format all your drives and reinstall the system from scratch.

The only glimpse of hope is the project called No More Ransom!, an initiative by Law Enforcement and IT Security Companies like Kaspersky or McAfee to help victims of ransomware recover their encrypted data without paying the criminals.

Make sure to visit No More Ransom website and use the tool to upload two files from your machine which will be used to define the type of malware and if lucky you will receive a decryption solution to download and run on your device.

Example of a notification window on the machine infected with WannaCry Ransomware.
An example of a machine infected with WannaCry ransomware.

Computer Worms.

A computer Warm is capable of infecting and spreading without user interaction. It often spread itself using the network, software or system vulnerabilities to cause damage or slow down the system’s performance. It may also install backdoors to allow hackers to gain access to the systems.

Where do computer viruses come from?

Like any other computer program, computer viruses are written using programming languages. With little learning, anyone can write a simple computer virus. The most challenging part is to learn how to infect the computer with the virus without alerting all the defence systems and avoid detection by the Anti-Virus software.

What are the symptoms of computer virus infection?

The computer runs slower.

You may notice a significant drop in your computer performance. Some computer viruses can multiply files filling up the disk space, which reduces your storage response time.

Of course, you may work with large files that take a long time to open, so keep in mind that slow response is not a definitive computer virus sign. But If your computer is not new, you should know by now what to expect from it in terms of performance. If the performance has dropped significantly, and there is no hardware fault, you should scan the system for malware.

Unexpected pop-up windows.

If you start to see popup windows with unknown links or unusual messages, it is time to scan your system for malware. The Windows operating system will use popup messages to notify you if you have an email or if your Anti-Virus software needs updating and so on. Pay attention to pop-up windows and click the links only if you know they are genuine.

Your system crashes frequently.

The Windows system may crash from time to time. However, more frequent failures may indicate damage to your hard drive data caused by a computer virus or other malware.

Your storage space runs low.

The computer viruses spread in the system infecting other programs and files; they may also download additional malicious software or files, decreasing the storage space.

Increased Network activity.

Make sure to check from time to time your network activity, especially when your computer is idle. The computer virus or other malware might use your internet connection to send and receive information. Check your Network activity using Task Manager and make sure your computer is left idle.

Your friends receive spam emails from your email account.

Computer viruses and other malware are notorious for trying to hijack emails. They then use the account to spread by sending emails to anyone within the contact list.

Your Anti-Virus software is disabled.

The primary defense against computer virus infections is your Anti-Virus software. If you notice that the Anti-Virus software is disabled or can’t be updated you should immediately take action. If you can’t activate the Anti-Virus software, contact their support team, and they should help you.

These are just a few symptoms of a system infected with a computer virus or other malware type.
You should know your computer like you know your car.
If you notice any unexpected events, you should investigate them. More often than not, it will not be malware but some system glitch or hardware failure but stay vigilant and pay attention to the signs, especially if notice a few of them at once.

How can I protect my computer from virus infection?

Use reputable Anti-Virus Software.

The first line of defense is a reputable Anti-Virus software which you should keep up to date and scan your system at least once a month.

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I have been using Bitdefender Total Security for years now, and I’m pleased with the software. I even took part in the Bitdefender Beta testing program. As a beta tester, I was able to influence the direction the software UI was developed for the final release.

But you can try any other Anti-Virus software like Kaspersky Total Security, McAfee Total Protection or Norton 360. It is entirely up to you which Anti-Virus software you will use as long as is up to date and that you frequently scan your system.

Don’t rely on your Anti-Virus to do everything for you. Interact with it from time to time. Check notifications which are often collected and may require your attention.

Image showing notification area in Bitdefender Total Security Anti-Virus software.
Bitdefender Anti-Virus software notification area.

I have mentioned earlier that my Anti-Virus software did not detect the Adware which I accidentally installed on my machine.

That’s where the dedicated software like Malwarebytes helped me to remove it. Malwarebytes was specifically designed to detect and remove any type of malware from your machine.

Malwarebytes software window.
Malwarebytes Software.

Don’t open unknown email attachments.

Unfortunately, when it comes to opening email attachments, we do this almost automatically, often realising after the fact that we should have first checked the email and the attachment carefully.

Try to develop a habit to remain on an elevated alert level every time you receive an email. It is not easy, but you will eventually start questioning every email in your mailbox and whether you should click that attachment.

Don’t use your computer as Admin.

Using your computer with Admin account is a high risk as it may allow the computer virus to spread without control due to elevated privileges.

Make sure to set up a standard user account with limited privileges for every person who uses the computer. Having an account with limited privileges will stop the virus from spreading and prevent anyone with access to the device from modifying your settings or viewing your files.

Keep your software up to date.

Authors of the computer viruses or any other malware will exploit any vulnerabilities found in your system or software to penetrate and infect your system.

Make sure to keep your system up to date and frequently check for any updates to the software you are using.

Make sure to scan removable media.

Computer viruses and other malware can be transferred to your computer via removable media like an external hard drive or flash drive.

Make sure to use your Anti-Virus to scan your external hard drive or flash drive every time you plugin into your computer.

Install browser popup blocker.

Simply browsing the internet may result in malware infection if you end up on a malicious site or click a dangerous ad or popup window.

Although you can configure your Anti-Virus software to track your online activity and stop or warn you before visiting malicious websites, they won’t stop you from clicking the popup messages.

The best solution is to install a popup blocker browser extension. The popup blockers are designed to suppress unwanted popups or overlays, making internet browsing safer and more pleasant.

Below are the links to the Popup Blocker for most commonly used browsers.

Keep Microsoft Office updated.

If you are Microsoft Office user, make sure to keep the software up to date. As highlighted by Kaspersky Security Bulletin 2020, the Microsoft Office package is the most popular target for cybercriminals who continuously try to exploit the known vulnerabilities in this software.

Be vigilant when opening Microsoft Office files from unknown sources. Cybercriminals will often embed malicious scripts in Word, Excel, or other documents types created in Microsoft Office.

Are all computer viruses harmful – Benevolent Viruses?

The American Computer Scientist Fred Cohen has been considering the viruses that perform useful tasks the so-called Benevolent Viruses.
For example, the Compression Virus may be responsible for file compression when little-used files are compressed and decompressed by the virus when needed.

Or the Maintenance Virus may perform maintenance tasks in the computer system by removing temporary files, stopping unneeded system processes or setting correct file permissions.

The other example is the Distributed Databases with viruses. The virus will spread and reproduce across networks performing searches and reporting back the results to the virus author.

How to remove a virus from a computer?

Download Anti-Virus Software.

If you don’t have Anti-Virus software, make sure to download one. You can try Bitdefender Total Security, this is what I’m using, but any reputable Anti-Virus should do the job.

Below is the list of some popular Anti-Virus software.

Disconnect the computer from the internet.

Now that you have Anti-Virus software, make sure to disconnect your computer from the internet to stop the virus from spreading and causing further damage.

Start the Windows System in Safe Mode.

The safest option to remove the computer virus is to start the Windows System in Safe Mode.

The Safe Mode is a special way to load Windows when there is a system-critical problem.

In Safe Mode, the system starts with minimal resources, most of the drivers are not loaded, and you will notice that the resolution is much smaller.

Starting the Windows System in Safe-Mode.

  1. Press Windows Logo + R on your keyboard.
  2. Type msconfig in the text field and press OK.
    1. Image showing Run command in Windows 10 to open msconfig.
  3. Under the Boot tab, select Safe Boot checkbox.
    1. Activate Safe Boot in Windows 10 msconfig.
  4. Restart the System.
  5. Remember to repeat this step and uncheck the Safe Boot option once you want your computer to start normally.

Alternatively, you can restart the computer and press F5 or F8, and select Safe Mode from the boot menu.

Delete Temporary Files.

Now that your computer is in Safe Mode, we have to remove Temporary Files which may contain the virus.

  1. Press Windows Logo + I on your keyboard to open the Settings.
  2. In the search bar start typing “Delete Temporary Files” then select from the list.
    1. Deleting Temporary files in Windows 10
  3. Now find and select Temporary Files.
    1. Selecting and removing Temporary files in Windows 10 Storage.
  4. Press Remove Files to remove the file categories that Windows has automatically selected as safe for removal or select additional categories and then press Remove Files.
    1. Remove files button in the Temporary Files category in Windows 10

Run a Full Virus Scan.

Now that we have removed all the temporary files which may have contained a virus file, you can scan the entire system using your Anti-Virus software.

I will not go through the details of how to scan your system using each Anti-Virus software listed above. Instead, I will show you how to use Bitdefender Total Security software to perform a full system virus scan.

Most Anti-Virus software has two options; Quick Scan and Full Scan, make sure to run a Full System Scan.

Open the Bitdefender Total Security and under Dashboard select System Scan.

Image showing Bitdefender Total Security Anti-Virus software System Scan option.
System Scan option available in the Anti-Virus software.

You will then notice that a new window has opened, indicating that the scanning is in progress.
At that stage, be patient as the process may take a while.

Image showing Anti-Virus software system scanning progress.
Bitdefender Full System scan in progress.

Delete or quarantine affected files.

Delete or quarantine any detected viruses and rescan your system, making sure no more virus are found.

Restart the computer.

Make sure to disable the Safe Mode before restarting your computer. See the “Start the Windows System in Safe Mode” section above and uncheck the Safe Mode checkbox before restarting.

Make sure to change your passwords.

This step may not be necessary, but you never know what type of malware you had and whether your passwords have been compromised.

Scanning for Malware with Malwarebytes.

Many people will stop here, but I will go a step further and use the specialised software like Malwarebytes to check for other types of Malware.

The free version of Malwarebytes will allow you to scan and remove any other Malware that your Anti-Virus software may have missed.

Format your Hard Drive and reinstall your Windows System.

Reinstalling the systems from scratch may sound like a very radical move. Surely after scanning the system with an Anti-Virus software and removing all infected files, the virus is gone, right?

Well, yes, it is.

But the Malware may have affected your system configuration settings before it was removed. For example, it may have created a Backdoor leaving your system vulnerable to other malicious programs.

It may also turn your computer into a Proxy allowing for internet traffic to go through your computer without your knowledge, providing anonymity to whoever uses it.

If that was my machine, I would have formatted the drive and reinstall the operating system.

How many computer viruses are found every day?

According to research performed by the Reason LABS, 224.360 viruses were detected in November 2020 alone. That makes around 7.500 every day.

Does resetting PC remove the virus?

Resetting your PC will now remove the virus. You have to use Anti-Virus software to remove the virus from the infected device and in some cases, even format your hard drive and reinstall the operating system.

Can a virus permanently damage your computer?

In most cases, the computer virus cannot physically damage your computer. However, in 1999 a virus called Chernobyl (Win95.CIH) destroyed data on the hard drive and BIOS chips located on a motherboard. Computers with damaged boot programs located on affected BIOS chips will no longer start and must be replaced and reprogrammed.

Can a computer virus infect a human?

Of course not, don’t be silly. (Or does it?).

My Favorite Software and Hardware.

Thank you for reading this article. I hope you found it helpful. Here is the list of the software and hardware I am personally using, which I believe you may also find useful. These are affiliate links, so if you decide to use any of them, I will earn a small commission at no extra cost to you. But in all honesty, this is the exact software I have installed on my computer and the hardware I have been using to secure my online accounts or store my passwords.

1Password Password Manager - I have been using 1Password for the past two years, and in my opinion, it is the best Password Manager yet. You can try 1Password for free or check the latest deals on the 1Password website.

Yubikey 5C NFC - This is a hardware authentication device that you can use to protect your online accounts or even computers. If you are thinking of getting one, I will highly recommend Yubikey 5C NFC, which, thanks to the NFC, can also be used with your phone.

Bitdefender Total Security - I had tried other Anti-Virus software whenever my Bitdefender license was about to expire. However, at the end of the day, this is still my favorite Anti-Virus. You can check the latest offers on the Bitdefender site.

NordVPN - If you are looking for some privacy when browsing the web, NordVPN will have you covered. Save 72% now with a 2-year planvisit the NordVPN website for more details.

Malwarebytes - It will defend you against harmful websites and remove any malware from your computer. Make sure to check the latest offers on the Malwarebytes website.