Something feels off about your computer. Maybe it is running slower than usual, strange pop-ups keep appearing, or your browser keeps redirecting to websites you have never visited. These are classic signs that your computer might be infected with malware.
The good news is that most infections are fixable, and many can be cleaned up at home with the right tools. This guide walks you through how to identify an infection, what to do about it, and how to protect yourself going forward.
8 Warning Signs Your Computer Is Infected
Not every slowdown is a virus — sometimes it is just an aging hard drive or too many startup programs. But if you notice several of these symptoms together, malware is a likely culprit:
- 1. Sudden, dramatic slowdowns. Your computer was fine last week but now takes forever to open programs or load web pages. Malware like crypto miners consume CPU and memory in the background, leaving little for your actual work.
- 2. Pop-ups appearing outside your browser. If you see pop-up ads or warnings on your desktop (not inside a web browser), your system is almost certainly infected. Legitimate software does not do this.
- 3. Browser redirects. You search for something in Google and end up on a completely different site, or your homepage has changed to something you did not set. Browser hijackers are among the most common types of malware.
- 4. Unknown programs appearing. You notice software in your Start menu or taskbar that you never installed. Some malware installs additional programs — toolbars, "PC optimizer" scams, or other junk software.
- 5. Your antivirus is disabled. If Windows Security or your antivirus suddenly will not open or has been turned off, sophisticated malware often disables security software as its first action.
- 6. High disk or CPU usage for no reason. Open Task Manager (Ctrl + Shift + Esc) and check the Performance tab. If CPU or disk usage is at 80-100% while you are not doing anything, something is running that should not be.
- 7. Friends receive strange emails or messages from you. If contacts tell you they received odd links or spam from your email or social media, your accounts may be compromised — often the result of malware capturing your credentials.
- 8. Ransom messages or locked files. If you see a message demanding payment to unlock your files, you have ransomware. Do not pay. Skip to the "When to Call a Professional" section below.
What to Do: Step-by-Step Removal Guide
If you suspect an infection, follow these steps in order. Each step is important — skipping ahead often leads to reinfection.
1 Disconnect from the Internet
Immediately disconnect your computer from Wi-Fi or unplug the Ethernet cable. This prevents the malware from sending your data to remote servers, downloading additional payloads, or spreading to other devices on your network.
2 Boot into Safe Mode
Safe Mode starts Windows with only essential services, which prevents most malware from running and makes it easier to remove.
How to enter Safe Mode in Windows 11: Hold Shift while clicking Restart from the Start menu. Go to Troubleshoot > Advanced Options > Startup Settings > Restart. Press 4 or F4 for Safe Mode, or 5 / F5 for Safe Mode with Networking (needed for downloading scanning tools).
3 Run Windows Defender Full Scan
Open Windows Security > Virus & threat protection > Scan options and select Full scan. This takes 30-60 minutes but checks every file on your system. Let it quarantine or remove anything it finds.
If Windows Defender Will Not Open
Some malware specifically blocks Windows Defender. If this happens, go directly to Step 4 — Malwarebytes can usually run even when Defender is disabled.
4 Run a Second-Opinion Scanner
No single antivirus catches everything. A second-opinion scanner finds what the first one missed. We recommend running both of these free tools:
Malwarebytes Free
The best free malware scanner available. It excels at catching adware, browser hijackers, and PUPs (potentially unwanted programs) that antivirus software often ignores. The free version is all you need for on-demand scanning.
Free (Premium: ~$45/year)
Download MalwarebytesRun a full Malwarebytes scan and remove everything it finds. If your computer is severely infected, you may need to run multiple passes — some malware reinstalls itself after being removed.
5 Clean Your Browsers
Even after removing malware from your system, browser hijackers often leave behind modified settings. For each browser you use:
- Go to Settings > Extensions and remove anything you do not recognize
- Reset your homepage and default search engine to your preferred options
- Clear all browsing data (cookies, cache, site data)
- Consider resetting the browser to default settings if problems persist
6 Change Your Passwords
If malware was on your system, assume your passwords are compromised. Change passwords for your email, banking, social media, and any other important accounts. Do this from a clean device (your phone, for example) until you are sure your computer is fully clean.
Use unique passwords for each account. A password manager like Bitwarden (free) makes this practical.
7 Set Up Protection Going Forward
Once your system is clean, take steps to prevent reinfection:
- Keep Windows Defender active — It is free, built-in, and genuinely effective in 2026. You do not need paid antivirus for basic protection.
- Enable automatic Windows updates — Many infections exploit known vulnerabilities that patches have already fixed.
- Be careful with email attachments and downloads — The vast majority of infections come from opening malicious email attachments or downloading software from untrustworthy sites.
- Use an ad blocker — uBlock Origin is free and blocks malicious ads that can infect your computer through your browser.
Avoid "PC Cleaner" and "Registry Optimizer" Software
Programs that claim to "speed up your PC" by "cleaning your registry" or "optimizing your system" are almost always scams. Many are actually malware themselves. Legitimate performance improvements come from the tips in our speed-up guide, not from registry cleaners.
When You May Need Professional Help
Some infections are beyond what home remedies can fix. Consider professional help if:
- Ransomware has encrypted your files. Professional recovery tools and techniques can sometimes decrypt files without paying the ransom. The sooner you act, the better the chances.
- Malware keeps coming back after you remove it. Some rootkits embed themselves so deeply that standard scanning tools cannot fully remove them. These require specialized tools and techniques.
- Your antivirus has been disabled and you cannot re-enable it. This indicates a sophisticated infection that has administrative access to your system.
- You suspect identity theft. If your financial accounts have been accessed or personal information stolen, professional cleanup ensures nothing is left behind that could enable further access.
- You are not comfortable doing this yourself. There is no shame in that. Incomplete virus removal often leads to reinfection, which wastes your time and puts your data at risk.
Protect Your PC Going Forward
Check out the security tools recommended above, and subscribe to The Technology Pulse for more guides on keeping your computer safe and fast.
Subscribe FreeHow Much Does Professional Virus Removal Cost?
Professional virus removal typically costs $75-$150 depending on the severity of the infection. That usually includes a full diagnostic, malware removal, system cleanup, and security setup to prevent reinfection. Ransomware recovery may cost more depending on the complexity.
Prevention: The Best Antivirus Is Common Sense
After years of experience, here is the bottom line: the most effective antivirus is careful behavior. Windows Defender handles the technical side perfectly well in 2026. What it cannot do is stop you from clicking a phishing link or downloading software from a sketchy website.
The three rules that prevent 95% of infections:
- Do not open email attachments from unknown senders. If it is unexpected, verify with the sender through a different channel before opening.
- Download software only from official sources. Go to the developer's actual website, not a third-party download site.
- Keep your system updated. Enable automatic updates for Windows, your browser, and your other software.