By Louis Adebajo

When we talk about VPN security, most people think about encryption and hiding their IP address. But there’s another critical element that often goes overlooked: DNS leaks. These leaks can quietly reveal what websites you visit, sometimes even when you are using a VPN.

One of the most recommended features to avoid DNS leaks is a Kill Switch. To understand the importance of a Kill Switch, it is essential to understand what a DNS leak is and why it’s a potential security risk.

This blogpost outlines what DNS leaks are, how a Kill Switch prevents them, and why solutions like Guardian Firewall + VPN include this essential feature.

DNS Leaks

DNS stands for Domain Name System. It allows you to translate a domain name into an IP address. Hence, every time you visit a website, your device uses the Domain Name System (DNS) to convert site addresses (e.g., google.com) into its allocated IP addresses. See Domain Name System. The use of a properly functioning VPN allows the following:

• All DNS requests should go through the VPN’s encrypted tunnel
• The VPN should define a trusted DNS server that is used at all times

A DNS leak happens when your device bypasses the VPN and sends DNS requests directly upstream to providers or anyone on the network that you are connected to, such as your ISP. This reveals the sites you visit, the time you visit them and potentially your approximate location. Even though the rest of your traffic may be encrypted, DNS leaks can expose some of your browsing activity as illustrated in the infamous Snowden case where it was discovered just how much information the NSA and US government had access to and were collecting across the world.¹

How a Kill Switch Operates to Prevent DNS leaks

The job of a Kill Switch is to make sure that if your secure VPN tunnel suddenly drops, your device is not able to send unprotected traffic out onto the internet.

In simple terms, If the VPN connection drops, your internet connection is immediately blocked, resulting in no network activity.

Here’s a step by step operation of the Kill Switch once it is enabled in your VPN settings:

1. Constant monitoring: The Kill Switch keeps an eye on your VPN connection in the background.
2. Instant reaction: If the VPN disconnects, even for a second, the Kill Switch immediately shuts down your device’s internet.
3. No DNS leaks allowed: This prevents your real IP address or DNS requests from slipping out to your internet provider or the provider of the network you are currently using.
4. Automatic recovery: Once the VPN reconnects, the Kill Switch restarts the internet and lets traffic flow again through the secure tunnel.

Why Guardian Firewall + VPN uses a Kill Switch to Prevent DNS Leaks

Guardian Firewall + VPN combines two layers of protection. A firewall that blocks trackers and unwanted connections and a VPN that encrypts your traffic. Because it performs both roles, blocking leaks is even more crucial.

Guardian Firewall’s Kill Switch feature provides protection in multiple ways

An additional layer of protection: Since network stability is not entirely guaranteed, the VPN and firewall alone can’t prevent DNS queries from slipping out when the service is disconnected. With the added complexity of having both a firewall and a VPN in one solution, the Kill Switch feature is essential when the VPN connection is temporarily unstable due to switching WiFi or network downtime. Without this protection, your device might unintentionally use regular, unencrypted DNS queries, potentially exposing your browsing activity.

Protection against tracking: Many Guardian users rely on our service to block trackers, advertising networks, and data brokers especially for sensitive activities such as online banking or work-related tasks. Since it is the firewall that blocks trackers and unwanted connections before they leave your device, it is important that all traffic must pass through Guardian for the firewall to work properly. Without a Kill Switch, if your VPN connection fails, there is a risk of trackers not getting blocked which means your DNS queries may be sent to a third party without your knowledge.

Network isolation for safety: With Kill Switch enabled, your device prioritizes your internet’s privacy over local convenience. This can isolate it from devices on your local network (like printers, NAS, or AirDrop) to prevent data leaking onto the LAN. Although this can be a problem for some users, we have explained how this can be handled in our help center article.

Varying use cases and a Kill Switch solution

Although an obvious detail, it is worth noting that a VPN’s protection is limited to an active network connection. The second it disconnects, even by accident, your data can be exposed on the public internet instead of being protected by encryption as expected. Hence, a Kill Switch can be said to be the circuit breaker for your device’s traffic.

From students and remote workers to lawyers, bankers, government agencies, healthcare providers, and IT professionals, everyone can benefit from using a kill switch feature to protect against things like unstable Wi-Fi, VPN dropouts, and ISP monitoring exposing sensitive data. The Kill Switch prevents identity leaks, protects confidential communications, secures financial transactions, safeguards patient information, and ensures safe access to critical systems across home, office, and public networks.

Whether you are using a VPN for general privacy or securing sensitive information, always ensure that your VPN includes a Kill Switch functionality. This simple, yet powerful feature offers peace of mind and ensures that your online activities remain private and secure. If privacy matters to you, a Kill Switch is highly essential.