Is it really a virus? Symptoms to check first

A slow or misbehaving PC is easy to blame on a virus, and some websites are built to make you think so. This procedure takes about eight minutes and only looks; it does not delete or change anything.

1. Write down what you noticed and when it started

   A short note now saves guesswork later. Record what is happening, roughly when it began, and anything that changed around then: a new program, a browser extension, a Windows update, or an email attachment you opened. Most problems trace back to something that happened that day.

2. Compare what you see with the signs of malware

   These symptoms are hard to explain any other way. One is worth acting on; two or more make an infection likely.

   • Your homepage, new tab page or search engine changed without your doing it.
   • Browser extensions or toolbars appeared that you did not add.
   • Ads appear on sites that normally have none, or pop up in the corner of the screen as notifications.
   • Windows Security says protection is off, and it switches off again after you turn it back on.
   • Friends receive emails or messages from you that you did not send.
   • You get sign-in or password-reset alerts for accounts you did not touch.
   • Files will not open, their names have a strange new ending, and a note demands payment.

3. Rule out the usual innocent causes

   These complaints are common, and on their own they almost never mean malware.

   If you notice	Then it is usually
   The PC became slow right after an update	Windows finishing background work. Leave it on and connected for an hour, then restart.
   A slow start and a long wait before you can work	Too many apps starting with Windows, or a nearly full drive. See the slow PC procedure.
   Fan noise or warmth during video calls or updates	Normal load, or dust in the vents.
   A web page says you are infected	A scam page. Windows does not report infections through websites.
   Crashes or a blue screen after a driver update	A driver fault, not a virus.
   Pages load slowly or Wi-Fi keeps dropping	The router or your provider. See the Wi-Fi procedure.

4. Check Windows Security

   Windows Security shows whether protection is on and whether it has already caught something.

   1. Select Start, type Windows Security, and open it.
   2. On the home page, look for a green check mark on each area. A yellow or red mark means something needs attention; select it to see what.
   3. Open Virus & threat protection › Protection history and read any recent entries.

   If another antivirus such as McAfee or Norton is installed, Windows Security names it; check that product’s own history instead. If protection is off and no other product is listed, see how to turn Defender back on.

5. Look for unfamiliar programs in Task Manager

   Malware has to run to do harm, so it usually shows up as a running process or a start-up entry.

   1. Press Ctrl + Shift + Esc. If Task Manager opens as a small window, select More details.
   2. On Processes, select the CPU column heading to sort by it. Note anything you do not recognize that stays near the top while the PC is idle.
   3. Open Startup apps (Windows 11, in the menu on the left) or the Startup tab (Windows 10). Note unfamiliar names, especially any with no publisher shown.

   Many genuine parts of Windows have odd names, so an unfamiliar name is not proof. To check one, right-click it and choose Search online. Do not end or disable anything yet; you are only collecting clues.

6. Check recent apps and browser extensions

   Unwanted software usually arrives bundled with something else. Look at what was added around the date in your note.

   • Windows 11: open Settings › Apps › Installed apps and set Sort by to Date installed.
   • Windows 10: open Settings › Apps › Apps & features and sort by Install date.

   Then check your browser’s extensions by typing one of these into its address bar: chrome://extensions in Chrome, edge://extensions in Edge, or about:addons in Firefox. Note anything you do not remember adding.

7. Choose the procedure that fits

   If you found nothing and the only problem is slowness, malware is unlikely.

   If you found	Then
   Files that will not open and a ransom note	Stop here and follow the ransomware first steps now.
   Signs from step 2, or unfamiliar processes or apps	Run a full Defender scan.
   A changed homepage, unwanted extensions or notification pop-ups	Follow the browser clean-up procedure.
   Windows Security will not open, or a scan will not run	Start the PC in Safe Mode and scan from there.
   Only slowness, noise or problems after updates	Work through the slow PC checks or the stuck update fixes.

   When in doubt, run the full scan anyway. It costs nothing but time, and it is safe to run on a healthy PC.