DNS Leak :- Causes, Fixes & How to Avoid Them

DNS leak

DNS is an acronym for Domain Name System which is the internet system used to convert or translate domain names to numeric IP addresses.

An IP address also called Internet protocol is a unique numeric label linked to each device connected to a computer system that uses the internet protocol for communications. 

The DNS is used to resolve human-readable hostnames and provide information about names. It is designed to bridge gaps between the internet websites and IP addresses. A DNS, in simpler terms, is more of an internet translator whereby it translates human-readable words to computer language.       


In the absence of DNS, our interaction with the internet would be quite hard since you would require a record of all the IP address of all websites which takes loads of storage. DNS allows you to access internet locations by their names. For instance, you can access Vpncop.com by just typing the word on the URL tab other than typing the IP address

What is a DNS Leak?

what is dns leak?

The use of internet has grown tremendously over the past few years. On the other hand, cybersecurity is getting shakier as more and more sensitive information tends to leak through the channels used to transfer data from one area to another. A DNS Leak is one of the insecurities you can expect when interacting on the internet.

DNS leak in technical terms refers to the security flaw that leaks DNS requests to the ISP DNS servers regardless of the efforts a VPN service provider puts in to conceal them.

If you are not familiar with technical terms, you ask yourself what an ISP, VPN, and a server is and what they do.

It is essential that you understand the above terms to get a clear picture of what a DNS LEAK is, what it entails, and how it affects your DNS.

ISP is an abbreviation for Internet Service Provider. They are companies providing internet and other internet related services like virtual hosting and building of websites, within a defined geographical area.

VPN (Virtual Private Network) is a service that forms a secure and safe encoded connection to a less secure system, such as the internet.

VPNs work to allow remote users and company branches to access cooperate applications while in different corporate regions safely and transfer data through secure tunnels without involving a third party.

They also secure corporate information as they apply authentication methods like passwords, codes, and unique identification processes before revealing the protected information.

Privacy is a primary focus when using the internet, and wherefore a VPN acts like a cop that guards your information against leaking and getting into the hands of internet goons.

Types of VPN  

Remote access VPN 

The above kind of VPN  allows its users to connect to them and access its private networks services remotely. Remote Access VPN is typically a secured connection between the user and the VPN. This type of VPN  is best suited for home use.

Site-to-Site VPN

Site-to-site VPN is best suited for cooperates. It is also called a router-to-router VPN.  Companies with offices at different geographical locations use this VPN to connect the networks between offices.

When numerous offices of the same firm link utilizing this type of VPN it is called an Extranet-based VPN.

A site-site VPN bridges the network gap between offices that are not within the same geographical area using the internet and still maintains a secure and private communication between the networks.

One router acts as a VPN client while the other acts as a VPN server. The interaction between the two servers only takes place upon validation and authentication of security.

The above categories of VPNs work on different VPN security protocol.

  • 1
    Internet protocol security/IPSec
  • 2
    Layer 2 tunneling protocol
  • 3
    Point to point tunneling protocol
  • 4
    Secure sockets layer
  • 5
    Open VPN
  • 6
    Secure Shell.

Now that you understand the standard technical terms used to define a DNS leak, you can simply define a DNS leak as a situation where the DNS searches leak to third parties like the ISP even when you employ measures like the use of a VPN to combat such occurrences.

Common Causes Of DNS Leaks

#1 VPN Server Corruption

DNS leaks may result when for some unintended error,  the VPN server fails to perform its purpose. For instance, a  DNS request may ignore or bypass the VPN servers. This error causes the DNS server operator to see your activities on the internet without your knowledge or consent. 

#2 Corrupted Windows Operating System

Using a corrupt operating system makes you more susceptible to the risk of a DNS leak. Windows, and especially Windows 8, Windows 8.1, and  Windows 10 have a feature called the “Smart Multi-Homed Name Resolution.”

 This feature is ideally supposed to increase your surfing speed. What it does is send out DNS requests to all available DNS servers and accepts the response from the fastest DNS server to respond.

This oversight presents a problem to VPN providers since these are default settings that the user is unlikely to be aware of or change.

VPNs have to work extra hard to plug this leak especially in Windows 10 because it not only exposes users to typical DNS leaks but also to DNS spoofing attacks.

#3 Introduction of IPv6

As you well know, the standard IP Address is an IPv4, 32-bit code that consists of 4 sets of 3 digits, for instance, Unknown to you is that availability of IPv4 IP addresses is becoming a problem. To deal with this predicament,  the internet introduced IPv6 addresses.

IPv6 IP address are made up of 128-bit,  8 sets of characters that can be made up of both digits and letters, for instance,123a.1b23.ab12.1ab3.a12c.1234.abcd.1a2b.

Not all the VPNs in the market can adequately secure IPv6 addresses. For the most part, they work better with IPv4 address. If your VPN does not protect IPv6 addresses or at least have the option of blocking IPv6 addresses, then you are at risk of a DNS leak.

#4 Use of Transparent Proxies 

Savvy ISP providers are now using transparent DNS proxies to engineer a DNS leak. They do this by intercepting all DNS lookups and forcing them to transparently proxy the results. All your DNS requests reroute to your ISP DNS servers which virtually bypasses all DNS filtering and forces a DNS leak.

Detecting a transparent proxy is a wise move. Ensure you ascertain if your ISP is among the ones that use a transparent proxy.

Checkout :- Proxy vs VPN

#5 Teredo

With the onset of IPv6 addresses into the market, there arose the need for a reliable transitional software to help integrate the IPv4 and IPv6 addresses to work together. 

As a result, Windows introduced the Teredo technology that allows IPv6 requests to be understood, accepted, and executed on IPv4 platforms.

However, to do this, the Teredo has to take precedence over a VPN protocol. Teredo uses tunneling similar to that of a VPN.

 When presented with both a Teredo and VPN request, the user’s server has to give priority to the Teredo which introduces the risk of DNS leak.

DNS Leak Problems And Fixes

When your DNS leaks, it affects your VPN in one way or another. Below are the top five common problems that arise as a result of DNS leaks

1.Configuration Problems

A DNS leak may occur due to laxity of transition from one network to the other mainly for users who are continually changing network systems.

For instance, a user who often switches from a home network to work to public WIFI like the coffee shop or a cybercafe is more at risk of a DNS leak than a user who uses a single network.

The DNS leak occurs in the delay before your VPN takes effect and as your device connects to the new network.


Ensure you assign a specific DNS server to handle all your DNS lookup requests. You can do so by setting the proper DHCP settings in your network options. Adequate DHCP settings ensure that all your DNS lookup requests run straight to the designated DNS server.

Also, consider the services of a VPN that has its DNS servers. VPNs without DNS servers cannot sufficiently counter this risk considering the availability of transparent proxies and other software that give priority to the fastest DNS servers.

A good VPN will ensure all DNS requests go through their DNS filters and servers to guarantee anonymity for the user.

2.The transition of IPv4 to IPv6

As earlier stated, the transition of IPv4 IP addresses to IPv6 is presenting a problem for VPN service providers. Favorite websites have both the IPv4 and IPv6 addresses, few have IPv6 only, while most have IPv4.

VPN service providers have the option of upgrading their servers to accommodate the IPv6 addresses. But it is an expensive affair so rather than upgrade, they leave them as they are and expose you the risk of a DNS leak.


Ensure that your VPN provider covers IPv6 addresses or has a feature that blocks IPv6 addresses. If you are using a free VPN, it is likely that you are not getting any coverage when it comes to IPv6 DNS leak protection. So consider subscribing for a paid VPN.

If you are already on a subscription-based VPN, check the details your VPN provider to ensure that they have dual stack protection. The dual stack protects both IPv4 and IPv6 addresses.

From the in-depth check of your VPN provider, ensure there is an explicit list of the servers that support IPv6. If you cannot access such detailed information, it is likely that the specific VPN provider does not offer IPv6 DNS leak protection.

3.Latest Insecure Window Features

In an attempt to increase the speed of browsing for its users, Windows 8, Windows 8.1, and Windows 10 have a feature known as the Smart Multi-homed name resolution.

The worst culprit is Windows 10 which optimizes speed by sending DNS requests to all available servers and then responds to the fastest one.

This feature is a significant problem because your DNS requests are available to not only your IPS DNS servers but also random hackers who happen to be hanging around better known as DNS spoofing.


Fixing this particular problem is simple. All you have to do is disable the Multi-homed name resolution setting. If you are using the Windows 10, you can disable it from the  Group Policy Editor.

This solution is, however, not adequate since the system will revert to the Multi-homed name resolution when all the other DNS queries fail.

Alternatively, there are several available plugins to automatically switch of the Multi-homed name resolution feature like the OpenVPN plugin by ValdikSS.

4.Teredo and 6to4

Teredo and  6to4 are the only two available routing standards that work for most of the Windows operating systems available on the market including 2007, 2008, Vista, and 2008 R2.

However, Teredo and 6to4 often require you to download and install drivers. Even so, they may still fail to work which can become frustrating in addition to the risk of DNS leaks.

That being said, you still need a solution that can work across both IPv4 and IPv6 systems in a protected environment that prevents DNS leaks.


The best way to work with both IPv4 and IPv6 systems securely is by use of IP-HTTPS and Microsoft DirectAccess.

Since Teredo and 6to4 configurations are a hassle to set up and still leave the user prone to exposure due to their habit of bypassing VPN DNS servers, the use of IP-HTTPS and DirectAccess is the only reliable solution to the DNS leak problem.

IP-HTTPS tunnels all traffic even IPv6 through the much-accepted HTTPS (SSL) stream. This way, you can access any data whether IPv4 or IPv6 without having to use Teredo or exposing your data to DNS leaks. IP-HTTPS provides secured tunneling even without the use of a VPN.

DirectAccess is the  App on Microsoft that allows secure transitioning of data through IPv6 and IPv4 systems.

5.Transparent DNS proxies 

Transparent proxies are used all over the internet because they make work easier and they require no configuration from the user.

Public internet outlets are especially prone to having transparent proxies working in the background without the knowledge or consent of the user. 

More sinister, however, are the transparent DNS proxy systems set up by ISP to monitor your activities on the internet remotely.

These force even VPN-protected servers to divulge the users surfing logs by intercepting DNS requests and forcing them to be serviced by their DNS servers.

An ISP has a lot to gain from your internet activities including bandwidth stifling and selling the information to third parties.


First of all, ensure you are not using a free VPN service. Free VPNs do not go the extra mile to try and protect you from DNS leaks.

Even with a subscription-based VPN, ensure you are using the latest version of the VPN. Modern VPNs, like OpenVPN, have their DNS servers and have found solutions to DNS leaks by allowing you to block outside DNS. By doing so, your DNS requests will only run through your VPN DNS servers and not any other.

Do your research before selecting a VPN provider to ensure they have systems to deal with DNS leaks concerning transparent proxies from the ISP.

How To Tell If You Have a DNS Leak

https://www.vpncop.com//guide-to-safe-internet-browsing/​​​It is imperative to find out if you have DNS leaks to take the necessary measures to plug the leaks.

There are numerous free tests offered on the internet to check if you have DNS leaks. The tests are pretty straightforward.

Once you compare the resulting IP addresses and match them to your own or your ISP’s, then it is very likely that you are experiencing DNS leaks. The best websites for providing free DNS leak detection include ipleak.net and dnsleaktest.com

As long as we are talking about DNS, it is worth mentioning that there is sometimes confusion between a Smart DNS and a VPN service. Users are sometimes at a loss and may think that using a Smart DNS is as good as using a VPN.

Well, VPN and Smart DNS are two different things.

A Smart DNS is a system that allows you to access geo-restricted content by changing your DNS. It does not offer any security or encryption to your data. All it does is make your DNS appear to be from a different geographic area to allow you to access otherwise restricted content.

A VPN is a set of systems that protect your internet activity by providing encryption and other security measures to ensure anonymity.

So in the case of dealing with DNS leaks, a Smart DNS will not do much to protect you, but a good VPN is a great asset to have.

Ways to Prevent Future DNS Leaks.

1. Change your DNS settings to a trusted or autonomous server

This step is the most comfortable and most affordable way to improve your DNS security. By manually changing your DNS server to a trusted autonomous one, you can ensure better safety as well as added benefits like:

You may end up with access to restricted content that you may not have gotten from your ISP DNS.

Servers like OpenDNS are free and offer extra protection against phishing.

You will enjoy added security measures not provided by your ISP DNS, for instance, Google DNS has DNSSEC automatically authenticates all DNS requests.

You can exert parental controls from these DNS servers to protect your children from adult content.

2. Enforce a Firewall Or Set Your VPN to Block Non-VPN Traffic.

A firewall is an Application which works within a network to monitor and control incoming and outgoing network traffic. You can use your firewall or IP Binding to block non-VPN traffic.

3.Test for DNS Leak Regularly

Regular DNS Leak checks will ensure that if there are any leaks, you will detect them early and take the appropriate measures. As earlier stated, there is various software available for checking DNS leaks. Even the free ones like dnsleaktest.com are reliable enough to tell you if there is a DNS leak in your system.

4. Use VPN Monitoring Software

In cases where your data and logs are extra sensitive,  consider the use of VPN monitoring software to see if there is a redirection of any of your DNS logs. Some monitoring software come at an extra cost besides the VPN subscription while others are part of the VPN package.

5.Select a VPN with DNS Leak Protection

Ensure the VPN you select has DNS Leak protection. DNS Leak Protection is not available on all VPNs, so it is essential to make sure yours provides DNS Leak protection before you make your purchase.

6. Immediately Switch Your VPN If You Notice Malicious Access In Your DNS

The internet is dynamic, and so you should learn to stay on toes when it comes to safeguarding your anonymity. Always be ready to change your VPN provider if they are no longer able to service your protection needs accordingly.

Also, ensure that your VPN is always upgraded to the latest version to counter the newest internet risks. Keep in mind that as hard as the VPN service providers work to protect you from the internet's bad actors, the hackers and phishers work just as hard to bypass the systems that are in place.

Here is a video explain about DNS Leak in Few Sec

Bottom Line

It is essential to understand that SSS/TLS encoding only applies to the content of communication between the user's local PC and the remote website. The recipient and sender addresses cannot be encrypted.

As a result, whoever has legal access to the DNS logs can visit all the destinations if need be.  In most developed countries the DNS Servers belong to the user’s ISP and are under the jurisdiction of the national laws. In countries like the UK and USA, law enforcement can acquire such data from ISPs on demand.

Also note, before you settle for any VPN service provider or subscription, be keen to check on how it functions and extra tools that come alongside the subscription. This insight will protect you from any risks that may lead to information leaking from your network.

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