What is a DNS Leak? [What it Means and How it Works]

Reading time: 6 min read
Aditya Rayaprolu
Written by
Aditya Rayaprolu

Updated · Sep 29, 2023

Aditya Rayaprolu
Technology Architect | McKinsey & Company | Joined February 2023 | LinkedIn
Aditya Rayaprolu

Aditya is an Azure DevOps and Infrastructure Virtualization Architect with experience in automation,... | See full bio

Ivailo Ivanov
Edited by
Ivailo Ivanov


Ivailo Ivanov
Content Writer | Joined October 2021
Ivailo Ivanov

If I was asked to describe myself using just a few words, I’d go with digital marketing expert, ex... | See full bio

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A DNS leak is a security problem affecting online privacy. This is an interaction between your computer and DNS resolvers.  

According to Statista, as of 2019, an estimated 1.01 billion internet hosts are available on DNS. These figures highlight how essential DNS is for internet browsing.  

If your DNS leaks, your online information can be stolen, such as what site you visit, what you input, and everything else online. 

Users must understand how to prevent this breach from compromising privacy and disclosing website visits. When your DNS leaks, this situation can be more dangerous than you thought.

Learn more about DNS leaks in the following section.

🔑 Key Takeaway

  • DNS leaks can make your online activities and private information public.  
  • This threat is dangerous as it can publicize your browser history. 
  • The leakage can allow other parties to view the history of the users.

DNS Leak Definition

The Domain Name System, or DNS, is responsible for finding the correct IP address when browsing. Users utilize DNS to locate valid addresses while conducting searches in the browser. 

Your Internet Service Provider (ISP) gains access to your history when your DNS leaks, allowing anyone with access to the DNS server to view everything you do online. 

In 2023, 25% of internet users will use VPNs, which are not 100% secure. In other words, there can still be leakage in your computer's DNS. 

💡Did You Know?

DNS can translate host names into IP addresses (forward DNS lookup) and IP addresses into domain names (reverse DNS lookup).

How Does DNS Leak?

DNS servers keep the user’s data, which stores information about IP addresses online. Your DNS will pose a severe threat if it leaks. 

Having someone spy on your online activities can be scary. They can steal your bank information, passwords, and confidential conversations. 


Here’s the explanation of DNS leakage according to NordVPN.

Continue reading the following segment to learn more about how DNS leaks occur. 

Understanding How DNS Leaks Happen

Understanding How DNS Leaks Happen

DNS leaks happen when a security flaw allows unnecessary parties to view the user’s browsing history. It can happen even when using a Virtual Private Network (VPN). 

It often happens when you enter data that translates the URL into an IP address that goes through outside the tunnel. With this, the Internet Service Provider would see your history. 

All the data, including your browser history, the location of your device, and other personal information. This is the reason why a DNS leak is dangerous. 

What Causes a  DNS Leak?

There are numerous causes for DNS leaks, which can occur at any time. It can happen even if you use a VPN server.

The leak can occur when the device has an improper configuration of the VPN or any privacy service. Continue to read about these common causes that led to DNS leaks. 

Having an Ineffective VPN Server

Using a VPN does not guarantee that you will have DNS. There are VPN services that do not have their own DNS servers.

Users may still experience the leak even while using VPN servers, primarily if the device still uses the default DNS server.

Transparent DNS Proxies

ISPs can use DNS proxies to force their customers to use DNS servers again. Users' web sessions would be redirected to DNS servers by the internet service provider. 

They often disguise this DNS to trick users into using the ISP's own DNS server. In this way, they could still see the user’s browsing history. 

Improperly Configured VPN

When a VPN is misconfigured, DNS is most likely to leak. Most VPNs require a user to connect to their ISP before logging in. 

Dangers of DNS Leak

When DNS servers fail, this will compromise your device. It would harm the user's data and online activities. 

Here are some samples of the dangers of DNS leaks. 

Privacy Threat

The primary concern with DNS leaks is the user’s privacy. With the leak, your online activities would be open to everyone. 

Your information could be compromised if your digital history were to leak. Malicious malware can infect your device if the leak happens. 

DNS-based Malware

There are a lot of viruses you can get from DNS leaks. Malware can use DNS features to launch attacks and insert ransomware into the device.

If the DNS leaks happen, it will make your device vulnerable to any malware. This means that DNS-based malware can infect your device more easily

Slower Computer Performance

DNS leaks also cause issues with your computer's performance. This can slow your internet connection as it constantly sends out DNS requests.

The DNS leak would also restrict the device's performance as it wouldn’t stop sending requests to the IPS servers. 

Malware Threats
This can also be dangerous, as you can connect to the wrong website. It might contain malicious malware that can infect your device. 

📈Market Trend:

Windows has long been regarded as the operating system with the greatest vulnerability and remains a profitable target for attackers, with a market share of roughly 51% worldwide

Prevention of DNS Leak

There are ways to prevent DNS leaks and protect your device. Users must know how to protect their DNS servers to avoid issues with their privacy. 

Here are some methods for preventing DNS leaks. 

Anonymous Web Browsers

Using anonymous web browsers can be a technique to avoid DNS leaks. This will give users total anonymity while browsing. 

Use Firewall

You can use firewalls to stop data from exiting your computer or control your DNS leak. Updating your firewall to protect your device against new threats is also essential. 

Run the DNS Leak Test

Running this test ensures that your browsing history and privacy are protected. Here is the method to check for DNS leaks and ensure your tunnel is not disrupted.

Step 1: Search for a free DNS leak testing tool and click on your chosen device. 

Step 2: The test would check the VPN used and see if your device is exposed. 

Screenshot of Your DNS Current Status

Step 3: Select Standard or Extended Test to check the DNS status. This would display your VPN leak test.

Screenshot of VPN Leak Test Prompt

Final Thoughts

DNS leaks happen when there is a fatal flaw in the device. The leak allows Internet Provider Service servers to see what users click on and search for online. 

Even though VPNs can protect your devices anonymously, leaks can still happen. This would occur if the user request was accidentally sent outside the encrypted tunnel.

The leak compromises the device's privacy even though the user uses the VPN tool. Understanding the process through which DNS leaks take place is crucial.


Is Cloudflare's DNS safe?

Yes, it is safe to use Cloudflare DNS, as their package includes DNS filtering and browser isolation. 

How does a DNS leak test work?

It works by sending several DNS records for the VPN to resolve. If one of the servers belongs to your ISP, your VPN might have a DNS leak. 

How do I clear the DNS cache on a router?

You can clear your DNS cache if you shut down or reboot your router. By doing this, it would prevent malware from attacking your device. 


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