How to Tell If Your Computer Has a Virus and What to Do About It (2024)

Computer viruses make your devices sick, but you can usually help them heal if you act fast.

Ever since the first malicious, self-copying computer code, named “Brain,” was unleashed back in 1986, viruses have caused headaches for many of us. Some viruses brick your devices and make them impossible to use, but more often viruses slow down your computer or steal your data. But there are steps you can take to boot a virus off your machine.

Since 2020, we have all likely become familiar with how real viruses, and computer viruses mimic disease-causing viruses like influenza or COVID-19. They are highly contagious and can easily jump from a computer to other devices or networks. When battling a computer virus, your poor device feels run down and requires more rest than usual – it probably has difficulty performing even the simplest of daily tasks!

Like the real thing, computer viruses replicate themselves, spreading through your operating system and network. At the same time, the virus is wreaking havoc: it can damage programs, delete files, and make devastating changes to your hard drive, all of which can result in reduced performance. Some viruses will even crash your entire system. Viruses can also give their cybercriminal creators a backdoor to destroy or steal your sensitive data and documents.

The idea of having a virus on your computer is scary, but we’re here to help! Here we’ve gathered tips on how to prevent, detect, and defeat computer viruses.

How does a computer get a virus?

The most common reason your computer will get infected is because you downloaded or installed infected files. Pirated media and free games are common culprits, and so are phishing attacks where you click on a bad link, button, or email attachment. Once clicked, the virus or other malware installs itself. Similarly, viruses can infect your computer when you visit scam websites. Sometimes, you can unintentionally install a virus from an infected external drive, like a USB stick.

How do I tell if my computer has a virus?

If you notice any or all these symptoms, your computer might have a virus and you should act:

• Suddenly slow computer performance, meaning it takes a noticeably longer time to start up or open programs
• Problems unexpectedly shutting down or restarting
• Missing files
• Frequent system crashes
• Frequent error messages
• Unexpected pop-up windows
• New applications (like web browser toolbars) that appear without you downloading them
• Overworked hard drive, which you can detect if your device’s internal fan seems to be whirring and working hard when you aren’t doing much
• Emails that send automatically from your accounts without you sending them
• Lagging web browser, or your web browser constantly redirects
• Malfunctioning antivirus programs or firewalls

I think my computer has a virus! What do I do?

If you think your computer has a virus, you should act fast to try to irradicate the malicious code. Don’t panic – we’ve broken down what you should do into a few easy-to-understand steps. If you can read this webpage from your device, you can probably save your computer and data.

1. Run a full-system scan

If you ever suspect your computer has a virus, use antivirus software to run a full-system scan of your device. It is best to set your antivirus program to do this automatically on a regular basis so you can detect any issues before they become emergencies. Review the detected threats and take any action that you can – many antivirus and antimalware programs guide you through this.

2. Restore to an earlier back-up

If you cannot delete the virus or infected files, try restoring your computer to an earlier back-up before you began having problems. Then scan your system again with antivirus software and see if the same issues exist.

3. Delete temporary files

Delete all the temporary files on your computer. How you delete these files is usually easy, but it depends on your operating system (like Windows or macOS). If you search for information for your specific system, you can find detailed information.

4. Go Safe Mode

If you are prevented from deleting files because your computer is malfunctioning, try booting up in “Safe Mode.” Safe mode restricts certain programs so you can work to fix the issue without interruption.

5. Reinstall your operating system

As a final measure to get rid of a computer virus, you can reinstall your device’s operating system (such as Windows or macOS). This can result in the loss of important files or other data. At this point, it is a good idea to take your device into a computer store and seek professional help. Many shops or experts will at least guide you through the process of reinstalling your operating system for free.

The only way to ensure that you eliminate a virus is to wipe your device and reinstall a new operating system on the machine:

• This is a good reason to practice good backup habits, because the process (called “reimaging”) eliminates everything on the hard drive (both the virus files and all of your files).
• Depending on the severity of the issue, you might be able to deal with malware or a virus without taking this step (by using a quality antivirus software or going into Safe Mode and removing bad files, for example). Still, if you want to be close to 100% sure that the virus is removed, reimaging is the most effective option.
• There have been rare instances where a computer virus even survives reimaging. If you are considering this drastic step, you should consult a tech professional.

How to prevent computer viruses

Just like with your immune system, an ounce of prevention is worth a pound of cure when it comes to computer viruses:

1. Use antivirus software

You should always have a trusted antivirus installed on your computer – it is best to boot up some antivirus software as soon as you start using a new device. You should be able to turn on regular scans of your entire device so you know if there are any issues ASAP.

2. Follow the Core 4

By following four basic cybersecurity behaviors, you can forge good habits that make it tough for computer viruses to get through:

• Use complex passwords that are at least 12 characters long and are unique to each account; use a password manager to securely store all your passwords
• Turn on multi-factor authentication (MFA, sometimes called 2-factor authentication) for any account that permits it
• Turn on automatic updates for your hardware, software, and apps
• Learn how to identify phishing – don’t take the bait!

3. Be careful on public wi-fi

Public wi-fi in cafes, airports, and other businesses can be convenient, but these networks are often unsecured and leave your phone, tablet, or computer susceptible to viruses. Using a personal mobile hotspot or VPN (virtual private network) is a more secure way to connect when you are on the go.

4. Get your software fresh from the source

One of the oldest tricks in the cybercriminal’s book is to sneak viruses and malware into software and files people want to pirate. Always download software from verified sources and get all your apps from your device’s official app store. You might think your saving some money by pirating software, movies, or other media, but you are also putting your expensive device and network at risk!