VPN: What is Kill Switch and should we really use it?

We find it on all the good VPNs on the market, but it is a function that we sometimes omit to start, often because we do not understand it well. And yet, it is essential to keep your confidentiality for sure when you “surf covered” with your VPN.

This function, called Kill Switch (or “emergency stop”, in good French) is indeed an essential safeguard for users who wish to remain discreet. This switch will indeed automatically block the Internet connection if the VPN is to flank … to restore it only when connection to the virtual private network will be restored.

Why is it so important? Because in the absence of an emergency stop, the exchanges between your machine and the server on which you are connected continue in the event of loss of connection to the VPN server. You are no longer hidden through the VPN: your real IP address is then exposed to the sites you visit, but also to any peers that share the same Bittorrent file that you are downloading, for example …

How does a Kill Switch work? It is rather simple, in truth: a service constantly monitors the state of your VPN connection: it thus performs a continuous monitoring of the state of the network interface, checks that your IP is that of the VPN server, and if the VPN service process is in function. At the slightest irregularity, the Kill Switch will immediately cut the connection and block all outgoing traffic, generally by modifying the rules of your system firewall.

In general, the best VPNs on the market offer two types of emergency stop. They first take advantage of a Kill Switch on the “system level”. It’s simple: as soon as the VPN connection is lost, the software will cut out the outgoing traffic from all of the applications running on the machine. It’s radical and very effective … but it can be frustrating if you use a VPN connection that tends to fall regularly. This is particularly the case with connection with exit servers in distant countries.

This is why the most efficient VPNs on the market also offer a Kill Switch function which offers more granularity: it allows you to cut the connection for the only applications you choose. We can, for example, only block the traffic of a Bittorrent customer.

On smartphone, whether on Android or iOS, the Kill Switch function works differently. Impossible, here, to make an app for app. On the other hand, the main mobile bones both offer a function of “permanent VPN”, accessible in the settings. This constantly activates the VPN connection. And this setting is supplemented by an option, which allows you to block connections when the VPN is off. Very effective!

The drawbacks of the Kill Switch

No technology is perfect, and the Kill Switch is no exception. A system emergency stop can be frustrating, especially when connection with the VPN server is not ideal (Wi-Fi problem, distant server), as it will regularly cut the Internet connection. It is especially boring if you are downloading a big file, where during reading a video stream. This is why, if your VPN suggests, it is better to use the blocking by application as far as possible.

Another problem: although VPNs have made great progress in the matter, using a Kill Switch can have slight consequences on the performance of your computer, since it permanently monitors your network connection. The impact is negligible on a powerful machine, but it can be notable if your computer lacks a RAM or has an inexpensive processor.

Finally, it is better to know: no Kill Switch is 100 %reliable. As shown by Tests carried out by rings.commost of the modern VPN emergency switches can leak data exchanges, especially when restarting the system.

In practice: Use the Kill Switch

The emergency stop function is not activated by default: you have to go to the parameters to activate it. Here, for example, how to launch the Kill Switch in NordVPN. From the main screen, simply click on the notched wheel indicating the settings. Go to the “Kill Switch” section then choose your settings.

Here you have the choice between several options. The first is the easiest to implement: it simply activates the Kill Switch if the VPN is unexpectedly disconnected. The second, more radical, offers you the possibility of cutting internet access as soon as the VPN is deactivated, even if you disconnect it by yourself. Practical for the heads-in-it!

NordVPN also allows you to use an application kill switch. Again, the procedure is simple: you just have to activate the function, then select the programs you want to leave when the VPN is not connected. Practical.

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