What is a DNS Leak? How Can I Prevent It?

cyber security

A domain name system or DNS resolves the alphabetic web address you put into your address bar and provides the browser with the IP address for the website. The browser then requests the page hosted on that IP address. Simply put, a DNS server points the browser in the right direction.

The process of translating the domain name into the corresponding IP address is called DNS lookup. IP addresses can be complex and a domain name makes things so much easier for everyone involved.

A DNS leak refers to a security lapse or vulnerability at any stage during the DNS resolution process. DNS leaks can be a serious problem and allow strangers and outsiders to eavesdrop on the traffic and the website as a whole.

To understand how a DNS leak happens and how it can be prevented, there are some things you need to understand first.

What is a VPN?

A virtual private network or VPN for short creates a tunnel between your device and the intended destination server. This allows it to securely transmit data and secures all traffic traveling between your browser, the DNS, and the host website server.

This keeps all activity anonymous and tracking is not possible. If due to some vulnerability, your ISP-provided IP address is exposed, you can be at risk.  

What is a DNS Leak? 

When your connection is not secure the whole stream of data traveling from your PC/mobile device to any website and back can be compromised. It goes without saying that you’re trying to mask your IP address and would like to stay anonymous when you use a virtual private network or VPN.

But sometimes VPNs do fail at hiding your IP address. The failure can reveal your original IP address, which in the wrong hands, can allow them to intercept the traffic between your browser and DNS. 

This exposure and failure to keep the IP address private is called a DNS leak. It allows prying eyes to intercept the communication between the DNS and your browser.

Is a DNS Leak Dangerous?  

In the wrong hands, a DNS leak can allow someone to:  

  • Trace your device’s IP address 
  • Allow access to the browser’s DNS requests thereby exposing the history
  • Allow access to your online activities  

This sensitive information can be used in all sorts of ways for targeted marketing or more sinister crime framing. The avenues for wrongful use are endless.

If you are not using a dependable VPN service like ExpressVPN there are chances that your ISP is already gathering this information about your usage. This is because your ISP DNS servers are being used instead of VPN servers.  

ISP servers are much less secure than a VPN server and can allow individuals to monitor your actions online by tracing your IP address.  

What Causes a DNS Leak? 

Your DNS comms can be compromised if: 

  • Your DNS settings are not configured properly 
  • ISP’s wrong use of DNS proxies
  • Faulty IPv4/IPv6 transition process

DNS Leak Test 

Good luck with keeping yourself safe if you’re trusting your ISP with your DNS privacy. But, even VPNs can sometimes fail at keeping things secure. To test if your VPN is protecting your DNS, follow the following steps: 

  1. Turn your VPN service off. 
  2. Head over to dnsleaktest.com or dnsleak.com.
  3. These websites will provide you with your ISP IP address, ISP’s name, hostname, and geographical location.
  4. Turn the VPN back on. 
  5. Select a different geographical location than the one you found in step 2.
  6. Access either of the websites again. 
  7. Compare the information obtained with the one obtained in step 3. 

It should show a different IP address. If the IP address is the same as before you have a potential DNS leak.

How to Prevent DNS Leaks?

You can prevent any leaks by taking preventive measures. These include:

1. Use a Dependable VPN  

The best VPNs keep the traffic secure and ensure that there are no DNS leaks. Make sure you opt for a service that offers DNS leak prevention. As an added layer of security, VPN monitoring software can also be used.

2. Regularly Clear DNS Caches  

Your PC also keeps caches of DNS information and your browsing history. To make sure the information doesn’t end up in the wrong hands:

  1. Press the Windows Key + R key combination and type in cmd.
  2. Type ipconfig/flushdns and press enter to flush DNS information. 

3. Disable Microsoft Teredo  

Microsoft Teredo can override VPN’s DNS servers and can result in a leak while trying to keep your connection stable. Teredo can be switched off through the following steps:

  1. Press the Windows Key + R key combination and type in cmd.
  2. Type netsh interface teredo set state disabled and press enter.

4. Make VPN’s DNS Servers Your Default Servers

Never allow traffic through the ISP servers if you’re worried about a leak. Always use a DNS provider that you trust. 

5. Use Secure DNS Service 

There are enterprise solutions for DNS communication protection. If you’re not satisfied with the level of security offered by the above-mentioned tips, a dedicated secure DNS service can be opted for. It monitors, filters, blocks, and manages DNS requests as the need may be boosting both security and productivity.

The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of The World Financial Review.