If the base filtering engine (BFE) is not running on your Windows device, the Proton VPN app will show the following error messages:

The most likely reason the BFE is not running is that a virus disabled it to perform malicious actions on your device.

For Proton VPN to work properly, you will need to restart the BFE.

We explain how you can reactivate the BFE below.

Windows 7

1. Open Start and type “services” into the search bar.

2. Click on Services inside the programs section.

3. Select Base Filtering Engine and then click Start. You should now be able to run Proton VPN without issue.

Windows 10 and Windows 11

1. Download the PsTools Suite.

2. Extract the zip file on to your desktop.

3. Go to Start and search for cmd → Run as administrator. (There will likely be a pop-up asking you if you want to let this app make changes to your device. Click Yes).

4. Open the extracted PsTools folder in the Command Prompt. (If you extracted the folder to your desktop, you can navigate to the PsTools folder by executing the following command in the Command Prompt window: cd C:\UsersYour User\Desktop\PSTools. Replace User with your Windows username.

5. Insidee PsTools folder, run the following command: psexec -s cmd.exe

6. No run: sc config BFE start= auto (make sure there’s an empty space between the = sign and auto).

7. Restart Windows. Once your device reboots, the BFE will be restarted and you should be able to use Proton VPN without issue.

If have followed these steps and are still experiencing difficulties, please contact our Support Team.