How To

Virus warning signs: How to tell if your computer has a virus

Computer viruses are an ongoing and evolving threat. Millions of computers in the U.S. are infected with malicious software – also known as malware – and new viruses surface regularly. And it’s possible for malicious software to infect your computer or device without you knowing.

But how can you tell if you’ve been a victim of a malware attack? There are several telltale signs your device may have a virus. We’ll share those red flags and outline steps you can take to get rid of the virus, and provide some tips to help protect your connected devices in the future.

How to tell if your computer has a virus

A computer virus is a type of malware that infiltrates a computer and its programs. It’s similar to the way the flu infects your body’s immune system and multiplies. Viruses can be installed on your computer without your knowledge or consent, and can insert new, malicious code that can monitor and manipulate your online activity.

Some malware may not seem serious, but they coud lead to more damaging problems. For example, criminals could use a virus to access to your personal information which could enable them to commit identity theft and other types of fraud.

You may be thinking you couldn’t possibly be affected. Or perhaps you’re wondering how bad a malware infection could be. The answer? Quite bad. For example, the MyDoom virus, discovered in 2004, is considered the most damaging virus ever released. Not only was MyDoom the fastest-spreading email-based worm, but it caused $38 billion in damage.

Ransomware is a another kind of virus that poses a threat. Ransomware entices its victims to click on a legitimate-looking link in an email that contains malicious code. The malware then prevents you from accessing your data by encrypting it. It holds that data hostage until you pay a ransom.

One example of ransomware was the destructive WannaCry virus of 2017, which targeted systems running Windows OS. Victims were asked to pay ransom in anonymous payment systems such as Bitcoin in order to retrieve their data. Keep in mind, even if you pay, you may not get your data back. That’s one reason why it’s recommended you shouldn’t pay the ransom.

Computer virus warning signs

Computer viruses are about as diverse as computer users. There could be thousands of new viruses and malware attacks each year and they can affect devices and operating systems in many different ways. But several virus warning signs tend to be similar across the board. Here’s how to tell if your computer may have been infected with a virus.

1: Major slow down of your computer’s performance

Are your files and apps taking a long time to load? Is your computer taking a longer time to start and runs slowly once it does? If so, it’s possible a virus is infiltrating your operating system.

2: Endless pop-ups and spam

Frequent and odd pop-up windows are a red flag. Pop-ups might prompt you to visit other websites to download antivirus or other software programs, which instead may install malware. Malicious pop-ups and spam could also secretly install spyware that could hijack your browser or steal your passwords and other personal information without your knowledge. When you finally catch on, it might be too late.

3: You’re locked out of certain settings, files, folders or your entire computer

If you’re unable to gain access to settings and files on your own computer — or you can’t log on or off — malware has likely taken over.

4: Changes to your homepage

Is your homepage randomly switching to another website? Are you unable to reset it? If so, you likely have a virus. Viruses can implement changes to your homepage and create error messages, browser errors and shortcut files.

5: Unknown programs start when you turn on your computer

Computer viruses can create widespread problems. Adding icons and toolbars that you didn’t set up is just the tip of the iceberg. If unknown programs load when you turn on your computer or other connected device, turn it right off again. You’ve been infiltrated.

There are different ways to find out what programs are running on your computer. On Windows machines, for instance, Task Manager is a utility included in Windows that shows you what programs are running on your computer. On a Mac you can find this in Activity Monitor.

6: Mass emails sent from your email account

Have you ever received an odd email from a friend that made you suspect someone hacked into their email account? Or you see people on Facebook and other social media platforms tell everyone they’ve been hacked and not to accept friend requests? If your email’s ‘Sent Items’ folder contains messages you didn’t send, your social media accounts have posts you didn’t make, or you can’t log into your email or social media accounts, your email and other accounts most likely have been compromised.

7: Your security software has been disabled

If your antivirus program or security software has stopped working and you didn’t disable it, it’s possible that malware has taken over.

8: Your battery drains quickly

Here’s another sign that a virus may have infected your computer and is multiplying: a drained battery. As the virus continues to multiply, it uses resources from your computer and creates more activity on your computer. As a result, your battery life is diminished.

9: Frequent crashes

Does your computer randomly crash on you? Does your screen freeze and become the infamous “Blue Screen of Death”? This is a could be a sign that your device has been infected with a virus.

What to do if your computer has a virus

You can take several steps if you suspect your computer has been infected. To start, you could get rid of the virus manually yourself. You likely will need to do a web search and perform a long list of steps to find out what’s really going on. Unless you’re an expert, it can be complicated.

A simpler approach is to install an antivirus software program from a reliable company. You can let the professionals do it for you to ensure you’re not leaving your computer open to any vulnerabilities. An antivirus program, also known as security software, may also scan your external hard drive when it’s plugged in, but keep in mind not every program checks the hard disk.

But when you do this, be sure you aren’t buying a program in response to an unexpected call or message. This could be a trick to download more malware.

Instead, go to a secure website that you trust. For example, a reliable security software is Norton Security, which can remove many viruses and help protect your Windows PC, Mac, Android and iOS devices against future infiltrations. Norton recommends a three-step virus clean-up plan:

Step 1: Run a security scan

You can start by running a free Norton Security Scan to check for viruses and malware.

Step 2: Remove existing viruses

You can then remove existing viruses and malware with Norton Power Eraser. It will perform a scan and give you onscreen instructions. If needed, you can call Norton for technical assistance. After following the instructions, restart your computer.

Step 3: Update security system

The most important thing you can do to help protect your devices against viruses and threats is to make sure your computer’s software is updated with the latest protections. When you’re notified of a Windows update or web browser update, for instance, it’s a good idea to install the latest version right away.

Then set your security software, web browser and operating system (such as Windows or Mac OS) to update automatically. This helps keep your operating system up-to-date and ready to detect and handle the latest viruses.

Once you’ve updated your software and secured your device with security software, there are simple and practical steps you can take to protect yourself, including these.

  • Reset the passwords to all of your accounts — and make sure they’re strong by including upper and lowercase letters along with numbers and symbols. Each account should also have its own unique password. A password manager can help you track and manage multiple passwords.
  • Use a pop-up blocker and be sure not to click on any unknown links or attachments.
  • Only download from sites you trust. Never download free software onto your computer, because it may be malware in disguise.

The bottom line? Don’t make it easy for cyberthieves to infiltrate your computer. Instead, keep an eye on your computer activity, be cautious about your own activity, and ensure you’ve updated your antivirus software and operating system with the latest protections.

It’s like wearing a mask or washing your hands during cold and flu season. Viruses may float around, but you’ll be helping to protect your system so they have a lesser chance of infecting you.


Symantec Corporation, the world’s leading cyber security company, allows organizations, governments, and people to secure their most important data wherever it lives. More than 50 million people and families rely on Symantec’s Norton and LifeLock comprehensive digital safety platform to help protect their personal information, devices, home networks, and identities.

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