How Your OS Is Working Against Your VPN

Alice Bonasio
Tech Trends
Published in
4 min readMar 28, 2020

The most common way for your VPN to leak your IP address is through DNS requests. Here’s what you need to know.

For the most part, a top-class VPN with built-in leak protection will help you avoid all the problems discussed below. If you’re not sure that your software has these protections in place, this simple to use VPN leak tool will tell you all you need to know in under a minute.

What Is a DNS Leak?

When you type a domain name into your browser (for example,, a Domain Name System (DNS) request is sent to your ISP’s DNS servers. This request results in that domain name being translated into an IP address, so your device can access that website.

The problem with your DNS requests going through your ISP is that they will know what websites you access, even if your IP is hidden by a VPN. Now, telecom companies are known to sell your browsing and location data (among other things); so you can see how that wouldn’t benefit you.

VPN providers mitigate this issue by having DNS requests run through their own servers, maintaining your anonymity. However, certain OS features will force those requests to go through your ISP under certain conditions, nullifying VPN protection in the process. Windows is the usual culprit, though Mac and Linux users shouldn’t rest easy.

Smart Multi-Homed Name Resolution

SMHNR for short, this mouthful of a Windows feature is tasked with speeding up the DNS request process. How does it do that? By sending out requests to all available DNS servers and selecting the one that responds the fastest. If your VPN’s DNS servers don’t respond quickly enough, your requests could end up going through to your ISP.

It’s possible to turn off the feature in Windows 8/ 8.1 and Windows 10 by following this guide. Keep in mind that Windows 10 Home users can’t access the Group Policy Editor without installing Policy Plus first. This free, open-source program adds Group Policy functionality to all Windows versions that lack it.

Teredo tunneling

VPNs work by routing your network traffic through an encrypted “tunnel.” This makes the encrypted data look like gibberish to…

Alice Bonasio
Tech Trends

Technology writer for FastCo, Quartz, The Next Web, Ars Technica, Wired + more. Consultant specializing in VR #MixedReality and Strategic Communications