Viruses and malware are a constant threat to PC users. Even with built-in security features and antivirus software, some threats still manage to find their way in. Knowing how to recognise the signs of a virus can help you act quickly before it causes damage or compromises your personal information.
In this article, you will learn the most common symptoms of a virus-infected PC, how to confirm whether your system is affected, and what to do if you suspect malicious software is at play.
Unusual Slowdowns and Poor Performance
One of the most noticeable signs of a virus is a sudden drop in your PC’s performance. If your computer used to run smoothly and now takes much longer to start up, load websites or open programs, this could be a warning sign. Viruses often run in the background and use up system resources without your knowledge.
While slow performance can be caused by many things, such as ageing hardware or too many startup programs, if the slowdown appears without explanation, it is worth running a virus scan.
Pop-Ups and Unwanted Ads
If your screen is suddenly flooded with adverts, pop-ups or fake warnings even when you are not browsing the internet, your PC may have adware or a browser hijacker. These programs are often bundled with free software and are designed to display intrusive adverts or redirect you to unwanted websites.
They may also try to trick you into clicking on dangerous links or downloading more malware. This kind of activity is a strong indicator that your system is infected.
Crashes, Freezes and Blue Screens
Malware can interfere with the normal operation of your computer and lead to unexpected crashes or freezing. In some cases, you might see the infamous blue screen of death more often than usual. If your system is restarting without warning or specific programs are failing to launch, this could suggest a virus is affecting your system files.
Always take note of error messages or behaviour changes and scan your PC if the problem becomes frequent.
Missing Files or Changed Settings
Viruses can cause files to go missing or corrupt system folders. You may also notice that settings have been changed without your input. This might include browser homepages, security settings or installed extensions that you do not remember adding.
If files are suddenly encrypted or renamed, you may be dealing with ransomware, which is a more serious form of malware that demands payment in exchange for restoring access to your data.
Strange Network Activity
Some viruses attempt to connect to the internet in the background to download more files or send stolen data. You may notice unusually high network usage, especially when you are not actively using the internet. This could result in slower browsing or higher data usage.
You can check for suspicious activity using Windows Task Manager or your router’s network tools. Any unknown processes using large amounts of bandwidth should be treated with caution.
Disabled Security Tools
A common trick used by malware is to disable your antivirus or block you from installing security updates. If Windows Defender or your third-party antivirus programme suddenly stops working, this may not be accidental.
Check your antivirus status regularly. If it fails to update or refuses to launch, you should suspect interference from a malicious source.
How to Confirm a Virus Is Present
The most reliable way to confirm whether your PC has a virus is to run a full system scan using trusted antivirus software. Windows Defender is built into Windows 10 and 11 and offers solid protection, but you can also use tools like Malwarebytes for additional scanning.
Make sure the antivirus definitions are up to date before running the scan. After the scan, quarantine or remove any threats that are detected. If your antivirus fails to launch, try booting into Safe Mode and scanning from there.
What to Do if Your PC Has a Virus
If a scan confirms that your PC is infected, take action immediately. Remove or quarantine any malicious files and run a second scan to check for anything missed. Change your passwords, especially for important accounts such as email or banking, in case they have been compromised.
If the infection is severe and cannot be removed easily, you may need to reset Windows or reinstall the operating system. Be sure to back up any important data first, but only if you are sure it is not also infected.
Final Thoughts
Knowing the warning signs of a virus can help you act before serious damage is done. By watching out for slow performance, strange pop-ups, missing files or broken security tools, you can identify problems early and deal with them before they spread. Regular scans and sensible browsing habits are your best defence against malware and viruses.