Many VPNs don’t block IPv6. If your ISP assigns an IPv6 address, and your VPN uses only IPv4, your torrent client may leak IPv6 traffic.
You’ve just found the perfect torrent. The download speed is blazing… but your VPN just disconnected without you noticing.
Suddenly, your real IP address is exposed to everyone in the swarm—including your ISP and copyright trolls.
This is exactly why the phrase is one of the most important Google searches a P2P user can make. Let’s break down what it is, why it’s critical, and how to set it up properly. What Is a Kill Switch (and Why Does Torrenting Need It)? A kill switch (often called a "network lock") is a safety feature found in most premium VPNs. It automatically cuts your device’s internet access the moment your VPN connection drops.
| Feature | App-level (VPN client) | System-level (firewall) | | --- | --- | --- | | How it works | VPN app blocks its own tunnel | Firewall rules block all non-VPN traffic | | Reliability | Good, but can fail if app crashes | Excellent, OS-level enforcement | | Torrent safety | Usually sufficient | Best-in-class | | Example | NordVPN, ExpressVPN | WireGuard + iptables, pfSense |