No, the genuine version is not a virus.
In fact, the real fsmainui.exe is designed to protect your computer from malware. However, virus creators sometimes name their malicious files after legitimate processes to hide in plain sight. fsmainui.exe
Here is a quick checklist to verify the authenticity of your fsmainui.exe: No, the genuine version is not a virus
| Verification Step | Legitimate | Suspicious |
| :--- | :--- | :--- |
| Digital Signature | Right-click file > Properties > Digital Signatures. You should see "F-Secure Corporation" or "WithSecure". | No signature, or signature from an unknown company. |
| File Size | Typically between 1 MB and 10 MB (varies by version). | Very small (under 100 KB) or unusually large (over 50 MB). |
| CPU/Memory Usage | Usually 0% to 1% CPU when idle. May spike briefly when opening the GUI. | Constantly high CPU or memory usage (over 20% for long periods). |
| Location | C:\Program Files (x86)\F-Secure\ | Desktop, Downloads, Windows folder, or Temp folder. | Solution: If the high usage persists for more
If you've uninstalled F-Secure but fsmainui.exe still appears in Task Manager, try these advanced steps:
While rare, sometimes fsmainui.exe will spike in resource consumption. This often happens during:
Solution: If the high usage persists for more than 10 minutes without a scan running, it’s likely a bug. Restarting F-Secure or your PC usually fixes it.