What’s a VPN kill switch, and how does it work?

You’re in your favorite cafe, sipping coffee while working online. Suddenly, your VPN disconnects without you realizing it. Normally, this might leave your browsing unsecured, meaning your activity could be observed by third parties like the internet service provider, the Wi-Fi admin, or attackers. But not if you have a kill switch.

A VPN is designed to protect your online privacy, and a VPN kill switch maintains that protection by instantly stopping all internet traffic going to and from your device if your VPN connection fails. This feature is essential for anyone serious about securing their personal information against inadvertent leaks.

However, while many VPN services include kill switches, they’re not all equally reliable. ExpressVPN sets itself apart with Network Lock, which is activated by default, providing a superior protective response that ensures your data stays secure—even if your internet connection becomes unstable.

Join us as we explore how kill switches work, discuss the different types available, and explain why Network Lock offers unmatched security that you can depend on.

What is a VPN kill switch?

A VPN kill switch is a feature that safeguards your digital activity from accidental exposure. Here’s how it works: While a VPN encrypts your internet traffic and shields it within a protective VPN tunnel, there are moments when the VPN connection might fail. When this happens, your device could automatically switch back to an unsecured internet connection, risking exposure of your IP address and data transmissions. If your VPN has a kill switch, it reacts to dropped VPN connections by cutting out the internet on your device entirely, so that you do not take the risk of an unprotected connection.

However, a proper VPN kill switch like Network Lock—available on ExpressVPN’s apps for Mac, Windows, Linux, and routers—does more than just react to connection interruptions. It also blocks any traffic on your computer from traveling outside of the VPN tunnel. This means that you are protected even if a malicious app or misconfiguration attempts to divert your traffic outside the VPN. If you have Network Lock enabled, your traffic will be blocked rather than be allowed to take a non-VPN route.

Why do I need a VPN kill switch?

You may not feel it necessary to turn on your kill switch if you are engaging in low-risk activities like scrolling on social media or browsing your favorite websites. In these cases, if your VPN connection drops, you’ll continue browsing as normal without a VPN until the connection is restored. 

But for situations where security is paramount or if you want as much privacy as possible, a kill switch ensures security, privacy, and peace of mind by taking you off the internet for as long as you are unprotected by the VPN.

Here are a few reasons to use a VPN with a kill switch enabled:

Identity protection

A kill switch shields your online identity by preventing exposure of your real IP address. This protects you from unwanted tracking and exposure of your real location, as your real IP address can be connected back to you.

Data privacy

A kill switch ensures consistent encryption of your data transmission. In the event of a VPN disconnection, it prevents data from potentially reverting to a non-encrypted state, thus protecting it from interception by third parties.

Prevent monitoring

In regions with internet censorship or monitoring, a kill switch is essential. It prevents your connections from defaulting to potentially monitored or restricted states, safeguarding you from surveillance.

Thwart attacks

Public Wi-Fi in places like coffee shops or airports might be unsecured, making you vulnerable to man-in-the-middle and other attacks. Ensure your online safety with a VPN, plus a kill switch that shuts keeps you off the internet if the VPN drops.

The different types of VPN kill switches

VPN kill switches are primarily categorized into two types: application-level and system-level, each suited for different security needs.

Application-level VPN kill switches

Application-level kill switches provide selective protection. They allow you to choose specific applications to disconnect from the internet if your VPN connection drops. This targeted approach lets you safeguard critical activities like browsing and banking, while less sensitive applications, such as music streaming, continue uninterrupted. However, this flexibility can come at the cost of comprehensive security, as non-selected applications remain unprotected.

System-level VPN kill switches

System-level kill switches offer the most robust protection by blocking all internet traffic if your VPN connection fails. This comprehensive approach is meant to guarantee that no data escapes your device outside the secure VPN tunnel, effectively preventing any potential data leaks across all applications. With these kill switches in place on desktop applications, any network traffic not routed through the VPN is blocked, ensuring your device never sends unencrypted data.

Which type of kill switch should you choose?

While application-level kill switches are suitable for users who want control over specific applications, system-level kill switches are generally recommended for their better security. They ensure that every bit of data transmitted on desktop applications is encrypted and secure, making them the best choice for those who prioritize complete privacy and protection. ExpressVPN’s Network Lock works as a system-level VPN kill switch, ensuring you are fully protected by blocking all traffic if your VPN connection drops. 

When does a VPN kill switch get activated?

A VPN kill switch activates automatically to protect your data whenever your secure VPN connection is interrupted. Here are the key situations that may cause this to happen:

• VPN connection drops: The most common scenario for kill switch activation is when your VPN connection suddenly drops due to server problems or connectivity issues.
• Switching between VPN servers: When you change from one VPN server to another, there may be a brief period when no VPN is enabled. The kill switch steps in during this transition to prevent any data leaks.
• Network changes: If you switch from one network to another, such as changing from your home Wi-Fi to mobile data, you might go unprotected by the VPN for a few seconds. The kill switch ensures that these transitions don’t expose your personal data.
• Malicious attempts at bypassing VPN: A kill switch takes action not just when VPN is dropped. It also responds when traffic tries to divert from the VPN tunnel. If malicious apps or misconfigurations attempt to drive your traffic outside the VPN, that traffic will be blocked by the kill switch.
• Device sleep and wake-up transitions: Devices can lose their VPN connections when they go into sleep mode or wake up. To prevent any accidental data exposure, the kill switch activates until the VPN connection is re-established.
• Unstable internet connections: An unstable internet connection could mean an unstable VPN connection. The kill switch will activate under such circumstances to maintain the security of your data.

Are VPN kill switches turned on by default?

Not all VPN providers enable their kill switches by default. But defaulting to “off” is a design choice that can pose a risk to users if they aren’t aware that they need to activate this security feature manually. The absence of an automatically enabled kill switch means that if your VPN connection drops unexpectedly, your data could leak without your knowledge, exposing your personal information and online activities.

The primary concern here is the accidental exposure of your real IP address and other sensitive data during VPN downtimes. These leaks are particularly problematic on unsecured public Wi-Fi networks, which would allow your activity to be seen by third parties. 

ExpressVPN’s proactive approach: Network Lock

Unlike many other providers, ExpressVPN’s Network Lock feature is enabled by default across all compatible platforms including Mac, Windows, Linux, and routers (on Android and iOS, we offer a feature similar to a kill switch called Network Protection). Network Lock immediately halts all internet traffic if your VPN connection drops, providing comprehensive leak protection, ensuring no data escapes. This default setting is a key part of our commitment to user safety, reflecting our dedication to providing robust, reliable protection without requiring manual setup. 

How does ExpressVPN’s kill switch work?

Network Lock goes beyond most kill switches by being proactive rather than reactive:

Robust firewall rules

Network Lock begins with a “block everything” firewall rule on all desktop platforms. A second rule then allows only VPN-routed traffic. These rules stay active through the entire connection cycle, including during reconnects and disruptions, ensuring consistent protection.

Comprehensive traffic management

Network Lock covers all types of network traffic—IPv4, IPv6, and DNS requests—to prevent any data from leaking outside the VPN tunnel. This total coverage ensures your personal information and activities remain private, even amid network instability or when switching Wi-Fi networks.

Should you ever disable the VPN kill switch?

While it’s advisable to keep the kill switch enabled to secure your data continuously, there may be specific scenarios where you might need to disable it temporarily. This might be necessary for troubleshooting connection issues or adjusting certain network settings. However, disabling the kill switch exposes you to the risk of data leaks if your VPN connection drops unexpectedly.

For these reasons, we strongly recommend keeping your kill switch active at all times, across all devices and VPN protocols, to ensure the highest level of data protection.

How to choose the right VPN kill switch 

It’s clear that a kill switch is an important part of maintaining your online privacy and security. So, before choosing a VPN, check whether a kill switch is offered and how it functions across different devices and operating systems. Here are key factors to consider:

Default activation

Check if the kill switch is enabled by default. A kill switch that requires manual activation might not protect you if you forget to turn it on. For example, ExpressVPN’s Network Lock is on by default, providing immediate protection without any additional setup.

Level of protection

Understand the level of security provided by the kill switch. It should ideally block all internet traffic if your VPN connection drops, preventing any data leaks. This is particularly important in environments where network stability is a concern.

Platform availability

Check if the kill switch is supported on all the devices and platforms you plan to use, such as Windows, Mac, Linux, and routers. If a kill switch isn’t available on a specific device, ensure there’s a comparable feature like ExpressVPN’s Network Protection in place.

User control

Consider how much control you have over the kill switch settings. You might prefer the ability to toggle the feature on or off depending on your specific needs.

Transparency and trust

Choose a VPN provider that’s transparent about how their kill switch works and the limitations it might have on different platforms. Trustworthy providers will provide detailed information about their security features, helping you make an informed decision.

Read more: ExpressVPN’s statement and assessment of the TunnelVision technique