What is a DNS leak? – GreenCloud

VPNs offer you security and privacy, ensuring that no one (not even your ISP) can see what you're doing online. But there is a security flaw known as a “DNS leak” that can expose all your web activity to your ISP – even if you use a VPN! In this short article, we'll try to answer some common questions about DNS leaks, explain what they are, how to check for them, and how to avoid them.

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What is a DNS leak?

A DNS leak is a security flaw that occurs when queries are sent to an ISP's DNS servers, even when a VPN is used to protect users. A VPN is designed to encrypt a user's internet connection, keeping their traffic in a private tunnel that hides all their browsing activity. This means that all of the user's internet searches and website visits are private to everyone except the VPN provider.

However, a DNS leak occurs when a user's DNS requests go outside the encrypted tunnel and appear for their ISP. As a result, all browsing activity, including IP address, location, and web searches, goes through the ISP just as it would if they weren't using a VPN.

How does DNS leak work?

The Domain Name System (DNS) maps domain names to IP addresses. What happens when you type example.com into your browser.

First, the browser will contact the DNS server and request the unique IP address of the site. Then the DNS server provides the IP address. The browser uses it to connect to the web server hosting example.com. Finally, the server sends the website data back to the browser, and you can view and interact with the site.

If you use the default DNS settings, your ISP or anyone with legal or illegal access to the DNS server can see what websites you want to access. Ideally, using a Virtual Private Network (VPN) helps keep your DNS queries private.

This means that your DNS requests are encrypted, routed through the VPN tunnel, and sent through the VPN service's DNS servers. So even your ISP can't track your online activities.

However, using a VPN is not 100% secure. Sometimes VPN servers leak DNS queries. Instead of encrypting DNS requests and routing them through a VPN server, your device sends them to another DNS server. This process is called a DNS leak and can create privacy issues.

Various reasons, such as misconfiguration or your VPN service not having its own DNS servers, can expose your DNS traffic to third parties.

Why is it dangerous?

A DNS leak can harm your overall online privacy. After all, no one wants third parties to check the sites they visit or the files they download. The biggest and most worrisome consequences of a DNS leak are:

Open browsing history: Unencrypted DNS queries contain some relevant information about you, including the sites you check and your approximate physical location. This ultimately compromises the privacy and anonymity provided by VPNs. Everyone from marketers to hackers can use them to create a profile of your online habits.
ISP tracking: If your DNS requests are leaked, your ISP can track and record your browsing activities. This data may reach third parties, including government agencies, and may even contribute to targeted ads (which means you'll see more of those annoying invasive ads).
Vulnerability to cyber attacks: Hackers can use DNS leaks to intercept, redirect, or manipulate your DNS queries. This could potentially lead to phishing attacks or malware infections. As a result, your personal or financial information may be exposed to unscrupulous individuals.

Do you have a DNS leak?

If you have a DNS leak, you probably won't be able to tell right away. Your VPN will appear to be connected to one of their servers and nothing will appear out of the ordinary. But behind the scenes, your browser sends DNS lookup requests to your ISP's DNS servers – which means they can see every move you make online.

The good news is that DNS leaks are pretty easy to test. There are many free, web-based services (such as dnsleaktest.com and ipleak.net) that will tell you if you have a leaking VPN. To run the test, first connect to a VPN and select one of its VPN servers. Then visit the DNS leak test website and follow their instructions to run the test. If you have a DNS leak, the test site should be able to detect it and notify you that your privacy is at risk.

How to prevent a DNS leak

There are many reasons why DNS leaks occur, and they may not be easy to fix. Below are some common troubleshooting methods.

Reset DNS settings. Simply restore everything to the recommended settings on your device.
Reset VPN DNS settings. Reset your VPN settings to the recommended ones.
Update your OS. Check your device for operating system updates and run them all. Updates contain security patches and should always be performed when they are released.
Change Internet browsers. Your browser may be giving you trouble, so switch to another one.
Connect to a different network. The problem may be connected to your provider. Try connecting to a different network.
Configure firewall settings to include DNS queries. Both soft and hard firewalls can be configured to include DNS queries. It is important to do this only if you are completely comfortable with what you are doing. Otherwise, contact authorized support.
Use a DNS proxy. This approach is a little more technical and involves manual configuration of firewalls or other proxy tools. We recommend restricting this approach to users with technical experience.
Use a different VPN. If you're using a lower-quality VPN, it may be time to upgrade. Higher quality VPNs have better DNS protection and technical support.

The result

DNS leaks, the corruption of data shared during internet requests, pose potential security issues for VPN users. Some common reasons for leaks include using a subpar VPN service, misconfigured VPNs and DNSs, and unauthorized third parties or apps to name a few.

The best way to arm yourself against DNS leaks is to use one of the most secure VPNs available. You should check your system regularly to make sure other issues aren't causing the leaks. Protecting your privacy leads to less spam and fraud, and even lowers your chances of identity theft.