VPN killswitches aren’t reliable, the best way to avoid exposing your IP address to your ISP is by binding the VPN network interface to the torrent client. Therefore you will only be able to download/upload while the VPN tunnel is active, reducing the probability of having a leak to virtually zero.
Requirements: A torrent client that supports binding, eg. qBittorrent (Windows, macOS and Linux) or BiglyBT (Android). The instructions below are for qBittorrent.
Method 1
- Open qBittorrent.
- Go to Preferences, and then Advanced tab.
- Check for the differences on the “Network Interface” list when you connect/disconnect VPN (you may have to restart qBittorrent for the list to refresh).
- Select (bind) the one that shows up/disappears from the previous test.
- Restart qBittorrent.
Method 2
Windows
- Start the VPN and connect to a location.
- Open qBittorrent. Go to Preferences, and then Advanced tab.
- Change Network interface to the VPN (usually its name, like “Mullvad”).
- Restart qBittorrent.
macOS
- Start the VPN and connect to a location.
- Open the Terminal app (it’s in Applications/Utilities).
- Run the command
ifconfig | grep -A 2 utun - Take note of the utun interface with the internal IP “inet 10.x.x.x” (eg. “utun3”).
- Open qBittorrent.
- Go to Preferences, and then Advanced tab.
- Change Network interface to the utun interface you found above.
- Restart qBittorrent.
Note: The utun interface may change if you reboot or reconnect.
Linux
- Start the VPN and connect to a location.
- Open qBittorrent.
- Go to Preferences, and then Advanced tab.
- Change Network interface to one of the following depending on the app and protocol you are using (Mullvad VPN as example)
- Mullvad app using OpenVPN: tun0
- Mullvad app using WireGuard kernel: wg-mullvad
- Mullvad app using WireGuard userspace: tun0
- WireGuard standalone: mlvd-xx
- OpenVPN standalone: tun0
- Restart qBittorrent.
How to test?
You can download the official Ubuntu 21.10 torrent and open it on qBittorrent. If the binding is properly set, the download will only start if the VPN is connected. If you disconnect, the download will stop.
The above guide was copied from Reddit user daiqo who posted it on r/VPNTorrents. I am reposting it on my blog for visibility, as Reddit might change its policies in the future.