7 Signs Your Computer May Have a Virus or Malware

Viruses and malware do not always make themselves obvious. Sometimes your computer continues working normally while malicious software runs quietly in the background. Other times, the warning signs are much easier to notice.

Strange pop-ups, browser redirects, unexpected programs, or a computer that suddenly becomes extremely slow can all indicate a problem.

Knowing what to look for can help you catch malware before it leads to stolen passwords, lost files, or additional damage.

1. Your Computer Suddenly Becomes Very Slow

Computers can become slow for many reasons, including limited storage, aging hardware, background programs, or Windows updates.

However, if your computer suddenly becomes noticeably slower without an obvious reason, malicious software could be using system resources in the background.

You may notice:

• Programs taking much longer to open
• Very high CPU or memory usage
• Your computer becoming unusually hot
• Fans constantly running at high speed
• Windows taking much longer to start

Do not immediately delete unfamiliar processes, though. Many legitimate Windows services have names that may not look familiar.

2. You Are Seeing Strange Pop-Ups

Occasional advertising while browsing websites is normal. Constant pop-ups appearing outside your normal browsing experience are not.

Be especially cautious if you see messages such as:

• “Your computer is infected!”
• “Microsoft has detected a virus.”
• “Call this number immediately.”
• “Your security subscription has expired.”

These messages are often designed to scare you into clicking a link, calling a fake support number, or installing unwanted software.

3. Your Browser Keeps Redirecting You

Another common sign of unwanted software is browser redirection.

For example, you may search for something on Google but clicking a result sends you to an unrelated website.

You might also notice:

• Your homepage changed without permission
• Your default search engine changed
• Unknown browser extensions appeared
• Websites automatically open by themselves
• Unusual advertisements appear in search results

These problems can sometimes be caused by potentially unwanted programs, malicious browser extensions, or browser hijackers.

4. Programs Appear That You Never Installed

It is a good idea to occasionally review the applications installed on your computer.

On Windows 11, go to:

If you see software you do not recognize, investigate it before opening it.

Unwanted applications can sometimes be installed alongside free software downloaded from the internet. This often happens when additional software is included during installation.

Not every unfamiliar application is malicious, so search for the program name before removing it.

5. Windows Security Has Been Disabled

Windows 10 and Windows 11 include Microsoft Defender Antivirus and several other built-in security protections.

Some types of malware attempt to disable these protections so they can continue operating without being detected.

Open:

Check the following areas:

• Virus & threat protection
• Firewall & network protection
• App & browser control

If security features suddenly become disabled and you did not change them yourself, the computer should be investigated.

6. Your Accounts Are Showing Suspicious Activity

Sometimes the first indication of malware does not appear directly on the computer.

You might receive notifications about:

• Password resets you did not request
• Login attempts from unfamiliar locations
• Emails being sent from your account
• Social media messages you did not send
• Purchases you do not recognize

Certain types of malware are specifically designed to steal passwords, browser sessions, cookies, and other sensitive information.

7. Your Files Have Changed or You Cannot Open Them

One of the more serious warning signs is unexpectedly losing access to your files.

You may notice:

• Files have strange new extensions
• Documents suddenly will not open
• File names have changed
• Entire folders appear missing
• A message demands payment to restore your files

These symptoms may indicate ransomware or another serious malware infection.

What Should You Do If You Think Your Computer Is Infected?

A suspicious pop-up does not automatically mean that your computer has been compromised. Start with some basic troubleshooting.

Disconnect From the Internet if Necessary

If you notice serious symptoms such as unauthorized account activity, ransomware messages, or suspicious programs actively running, disconnect your computer from Wi-Fi or Ethernet.

Run a Windows Security Scan

Open:

You can also use Microsoft Defender Offline Scan for threats that are more difficult to remove.

Check Installed Programs and Browser Extensions

Look for software or browser extensions that appeared around the same time the problem started.

Research anything unfamiliar before removing it.

Update Windows

Security updates help protect your computer against known vulnerabilities.

Go to:

Change Important Passwords

If there is any possibility that your passwords were compromised, change them from another trusted computer or mobile device.

Start with your email account because email is commonly used to reset passwords for your other accounts.

Be Careful With Fake Tech Support Pop-Ups

One common scam starts with a frightening browser message claiming that your computer has been hacked or infected.

The message may provide a phone number supposedly belonging to Microsoft, Apple, or another technology company.

After you call, the scammer may ask you to install remote-access software that allows them to control your computer.

Never give remote access to someone who contacted you unexpectedly through a pop-up, phone call, text message, or email.

How to Reduce Your Risk of Malware

A few simple habits can greatly reduce your chances of an infection:

• Keep Windows and your applications updated
• Keep Microsoft Defender or another reputable security solution enabled
• Avoid downloading software from unknown websites
• Be cautious with unexpected email attachments
• Do not reuse the same password across multiple accounts
• Enable multi-factor authentication
• Back up important files regularly
• Never give remote access to unknown callers

Need Help With a Suspicious Computer?

Sometimes it can be difficult to determine whether a computer problem is caused by malware, Windows, failing hardware, or another issue.

Nikasa IT Solutions provides computer troubleshooting, virus and malware removal, performance optimization, and computer support for home users and small businesses in North Vancouver.

We can investigate the problem, explain what is happening, and recommend the most practical solution.