Signs Your Windows PC Has Malware

By Malware-Bytes.net Editorial Team · Published 2026-08-12 · Updated 2026-08-28

Strong indicators

• Browser homepage or search engine changed without your input
• Pop-ups appearing outside the browser, or on sites that normally have none
• Unfamiliar programs in the Start menu or Task Manager
• Security software disabled and refusing to restart
• Files renamed with an unfamiliar extension, plus a ransom note
• Contacts receiving messages you did not send

Weak indicators with ordinary explanations

What to check first

1. Task Manager → Processes, sorted by CPU and network usage.
2. Task Manager → Startup for unfamiliar entries.
3. Browser extensions.
4. A threat scan — see how to scan Windows for malware.

Frequently asked questions

Can malware hide from Task Manager?

Yes. Rootkits and some injected threats hide processes, which is why a scan with rootkit detection is a better test than visual inspection.

Keep reading

• How to Remove Malware From WindowsThe full cleanup workflow, including stubborn cases.
• How to Detect Malware on a Windows PCManual checks that complement a scan.
• Malwarebytes ScannerScan types, timings and how to read the results.
• Malwarebytes Virus RemovalA start-to-finish cleanup process for an infected PC.

Malware-Bytes.net is an independent information resource about malware protection for Windows. We are not Malwarebytes, and this site is not the official Malwarebytes website or support channel. Malwarebytes is a trademark of Malwarebytes Inc.