What Is a DNS Leak?

DNS

Many people seek answers to the question, “What is DNS leak?” on Google. A DNS leak does not seem like a big deal to many people around the world. (“I have nothing to hide if I’m not doing something wrong, right? (This is incorrect.) However, depending on their country of residence and its rules, a leaky DNS is a major concern for some citizens.

When you type the domain name of a website into the address bar, the browser opens the website in a matter of seconds. However, there are several processes that go on in the background that you are unaware of. And if any of those methods has a security flaw known as a DNS leak, third parties will be able to spy on your entire browsing history.

  • What is a DNS and how does it work?
  • What is a DNS leak and what causes it?
  • How to perform a DNS leak test to tell if your DNS is leaking
  • How do you prevent a DNS leak?
  • What risks are associated with a leaky DNS?

What Is a DNS?

We’ll keep this brief because the purpose of this article isn’t to clarify what a domain name system (DNS) is (though it is important to understand the topic). You will skip this section if you already know the fundamentals.

Anything connected to the internet (including your computer, smartphone, and organization’s web servers) has a digital identity that can be written in numeric or alphanumeric format. An internet protocol (IP) address is what this is called. IP addresses come in a number of formats, including public, private, static, and dynamic, and are written in a variety of ways depending on their duration.

  • A numeric 32-bit IPv4 address is made up of four numeric segments separated by cycles. As an example, the IPv4 address for google.com is 64.233.166.113.
  • A 128-bit IPv6 address is alphanumeric, so it’s a lot bigger. Each of the eight 16-bit hexadecimal blocks in this form of IP address is separated by colons. Google.com’s IPv6 address looks like this: 2607:f8b0:4002:c08::8a; 2607:f8b0:4002:c08::8a; 2607:f8b0

So, if you want to link to a website, you must give the web browser the IP address of that website. However, as you can see, there are a lot of random numbers and letters to recall.

Remembering IP addresses for thousands of websites is inconvenient and almost impossible for the average human brain. The domain name system (DNS) technology comes in handy in this situation. DNS effectively converts the domain address of a website into an IP address for you.

The domain name system (also known as the “domain name service”) is a collection of servers and computers that connect domain names to their IP addresses (either IPv4 or IPv6). A DNS lookup is used to achieve this. Instead of entering a sequence of apparently random numbers any time you want to shop on Amazon, simply enter “amazon.com.” This straightforward approach makes details far easier to recall.

How Does DNS Work?

In a nutshell, the domain name system acts as a middleman between you and the website you’re trying to access.

  1. When you type a website’s name into your web browser, such as Amazon.com, the browser must look up the website’s IP address in order to open it. As a result, it makes requests to DNS servers in order to locate the IP address. Your internet service provider sends this request (ISP).
  2. The DNS server consults its cache and returns the website’s IP address to your browser through its DNS cache memory. If the DNS server can’t find it in the cache, it uses recursive resolvers, root nameservers, TLD nameservers, and authoritative nameservers in a four-step process. (For more information, see DNS servers.)
  3. After all of this, the DNS sends the browser the corresponding IP address of the website you’re looking for. The browser establishes a connection to the server that hosts the IP address (website). As a result, the DNS functions similarly to a phonebook or archive. It searches for a website’s IP address based on the name you gave it.

What Is a DNS Leak?

Now that we understand what a DNS is and how it functions, we can address the question, “What is a DNS Leak?” In a nutshell, a DNS leak refers to data leakage that happens despite the use of a virtual private network (VPN). Third parties can see the DNS server requests in general.

A virtual private network (VPN) is software that masks your original IP address and replaces it with a new random IP address that changes periodically. It also builds an encrypted tunnel that safely transmits all traffic between your browser, DNS, and the website’s server! As a result, your IP address cannot be used to monitor your online activities.

However, VPNs do not always succeed in masking your IP address and encrypting your communications. This causes DNS leaks because they expose your original IP address (provided by your ISP) to anyone who can intercept traffic between your browser and DNS.

What Does a DNS Leak Mean in Terms of Privacy and Security?

So, even though you’re using a virtual private network, a DNS leak means that someone can intercept communications between your browser and DNS or steal data from a DNS cache (VPN). This is often referred to as an IP leak.

But what good does it do to steal this kind of information? It means that intruders have the ability to:

  • Trace your device’s IP address,
  • See what types of sites you visit (based on your browser’s DNS requests), and
  • Monitor all your online activities.

But, wait, don’t your ISP’s DNS servers keep track of your DNS requests already? Yes, if your ISP’s DNS servers are used instead of the VPN’s DNS servers by default. That’s because browsers need the internet to communicate, and if the VPN isn’t configured to use its own servers, the ISP (and its DNS servers) will do so by default. Through tracing your IP address from browser-IPS DNS messages, your internet provider — and anyone else who can legally (or illegally) access their servers — can track all of your online activities.

What Causes a DNS Leak?

There are a variety of explanations why you may have a DNS leak. DNS leaks can be caused by a variety of factors, including:

  • The DNS settings on your network are wrong or misconfigured.
  • Transparent DNS proxies can be used by your ISP.
  • There are problems with your IPv4 to IPv6 migration.

A DNS leak isn’t amusing, to say the least. But how do you know if your DNS server is leaking data?

How to Conduct a DNS Leak Test

As previously mentioned, all traffic between your browser and the DNS server is unencrypted by default. (It’s sent in plaintext format, which means everyone can read it.) When this contact is intercepted, your ISP and any hacker can easily monitor all of your online activities.

However, if you’re using a VPN and suspect a DNS leak, you should take these precautions.

  • Disconnect from your VPN.
  • Go to dnsleaktest.com or dnsleak.com and type in your domain name.
  • Take note of the details that appears on the website as a result of your actions. This will be your ISP’s IP address, as well as the ISP’s name, hostname, and geographic location.
  • Switch on the VPN and choose any other geographical position you want.
  • Return to the DNS leak testing website and run the test once more. This time, you should be able to see the various IP addresses, names of internet service providers, and geographical locations. If you can still see your original ISP’s IP address and other details, your VPN has a DNS leak.

How to Prevent DNS Leaks

DNS traffic and data, as we all know, are vulnerable and unencrypted by nature. This means that unless you go to court, you won’t be able to stop your ISP from monitoring your activities and selling the data to advertisers if you use their DNS servers (we’ll go into the risks of DNS leaks later). However, there are several measures you can take to avoid DNS leaks.

Let’s take a look at how to avoid a DNS leak step by step.

Use a Robust VPN

The easiest way to mask your original IP address and encrypt the tunnel between your browser and DNS servers is to use a stable and reliable VPN. However, in some cases, browsers bypass the VPN’s IP address and send DNS requests to your original IP address. DNS leaks occur as a result of this. As a result, when using a VPN, keep the following tips in mind:

  • Activate the DNS leak protection function. You should always check whether a VPN has a DNS leak prevention feature before buying it.
  • Use VPN surveillance tools. VPN monitoring software keeps an eye on key indicators to ensure the VPN connection’s integrity. They ensure that all DNS requests are routed through a VPN tunnel and that the user’s original IP address is not revealed.

If anyone attempts to bypass the VPN IP address, it will automatically block the requests or warn the users.

Clear DNS Caches

All of your browsing history is saved in the DNS cache. If it is intercepted, an attacker would be able to monitor all of your online activities. As a result, flushing the DNS cache on a regular basis is recommended.

To clear your DNS cache on Windows, follow these simple instructions:

  • Go to the Start menu and type cmd into the search box. Open a command prompt window.
  • In the prompt, type ipconfig/flushdns.

Disable Microsoft Teredo

Microsoft Teredo is a technology that allows Windows-based devices to smoothly migrate from IPv4 to IPv6. Teredo assists in providing complete IPv6 access to hosts on the IPv4 Internet before all hosts are on IPv6.

While this is a useful function in certain situations, it is not without flaws. It also accesses the ISP’s IP address instead of the VPN’s, resulting in DNS leaks. You can, however, switch teredo off manually by following these three steps:

  • Go to the Start menu and type cmd into the search box.
  • Right-click the icon and pick Run as administrator when the command prompt appears.
  • Type in the following command: netsh interface teredo set state disabled.

Whenever you want to resume using Teredo again, type netsh interface teredo set state type=default into the command prompt to enable it.

Change Your Settings to Default to Use Your VPN’s DNS Servers

Your ISP won’t be able to monitor your activities if you don’t use the default IPS DNS server. Instead, you can use the VPN’s DNS api. Alternatively, if you want to use a public DNS server, just use a DNS server provider that you fully trust. Take a look at this website: What is the easiest way to use Google’s DNS server?

Use Secure DNS Service

Some enterprise-level solutions, such as Comodo’s Secure Internet Gateway, include a protected DNS link. To avoid leaks, it encrypts all DNS traffic. This tool also serves as a DNS filtering service in addition to preventing DNS leaks. It keeps track of all DNS requests and blocks malicious pages. To boost employee productivity, you can change the settings manually and block non-work-related websites.

Why Is a DNS Leak Dangerous?

It does not seem to be a big deal to many people. A DNS leak, on the other hand, may be a big deal for people who are concerned about their privacy or reside in areas of the world where such internet-related practises are prohibited. DNS records may be used for a variety of purposes, including censorship, monitoring, restricting internet use, and even legal penalties. So, if you’re using a VPN to access material that your government has blocked or limited, DNS records might be used against you.

There are other privacy-related problems that may arise from DNS leaks for people who don’t have those kinds of concerns. Your Internet service provider, for example, will sell your browsing data to marketers and advertisers. They closely track all of the websites you visit, learn about your interests and purchasing habits, and tailor ads to your tastes in order to influence your purchasing habits.

There’s also the issue of cybercrime to consider. For example, if a hacker obtains your information through DNS leaks, they can use it to threaten you with sophisticated email phishing attacks. They may also build watering hole phishing websites to threaten you and your coworkers if they know you or any of your coworkers regularly visit specific sites (such as a vendor’s website).

Isn’t that a terrifying thought? With the aid of a hypothetical example, let’s look at how hackers use your browsing history for phishing attacks.

Your DNS Request Data Could Be Used as Phishing Email Fodder

Let’s say an attacker takes advantage of your leaky DNS and intercepts your DNS request info. They notice how much you visit Chase Bank’s website. They can’t see your qualifications or other personal information because of the bank’s TLS/SSL certificates, however they can see that you visit Chase bank’s website and web pages related to student loans regularly.

Yes, that’s it! The hacker is aware that you are at least curious about loans and might even be considering applying for one. As a result, the intruder sends you a sophisticated phishing email that uses Chase bank’s logo and writing style to look as if it’s part of the bank’s loan approval process. They ask for your social security number, bank account number, and other personal information in the email!

You should not hesitate to make such a request after visiting the site and applying for the loan. As a result, it’s not unusual for people to fall prey to such schemes.

Your Data Could Be Used for Malvertisement-Based Cyber Attacks

Malvertising refers to malware-infected ads that attackers use to infect victims’ computers with viruses, trojan horses, worms, and other malware. Malvertising attacks may use DNS leak data to target people who visit specific websites.

Let’s look at another scenario. Let’s say a hacker intercepts your DNS cache and finds that you’re constantly visiting websites that provide tips on how to improve the speed of your mobile phone. To entice you in, the hacker might place an advertisement on that website that says, “Is your phone getting slow? It’s likely that it’s tainted with a virus. Now is the time to scan your phone with this free antivirus app to find and delete viruses!”

If you click on that ad, malware could be downloaded to your computer automatically.

DNS Data Is a Great Social Engineering Resource for Cybercriminals

Scammers use social media and other resources to collect information about you in order to plan a cyber assault in social engineering attacks. With a DNS leak, a hacker will learn about your preferences and the types of people you associate with by tracking the sites, groups, and profiles you visit on social media. The information is then used to:

  • Guess your username and password.
  • To connect with you and encourage you to share your personal information, create fake profiles/groups.
  • In your inbox, give you malware-infected files or attachments.
  • Send you links to pages that are spammy or malicious.

Advertisers can also monitor your social media habits and serve you ads based on your preferences. In short, advertisers and hackers are much more interested in your browsing habits than you may think!

Final Thoughts on DNS Leaks and How to Avoid Them

DNS, like every other technology, is not without flaws. Intruders (both hackers and advertisers) can easily obtain useful information about you from the web pages you visit thanks to a DNS leak. They have access to a wide range of data, including your:

  • Bank,
  • School,
  • Workplace,
  • Favorite ecommerce sites,
  • Insurance company,
  • Likes, dislikes, and
  • areas of interest,
  • Concerns you are facing (or may be seeking solutions for), and
  • People you communicate with on social media.

Hackers may use this information to carry out sophisticated phishing attacks, spread malware, and plan ransomware attacks as advertisers craft their advertisements to exploit your purchasing conduct. To avoid DNS leaks in the first place, you can always use strong VPN tools and other preventative measures.

Melina Richardson is a Cyber Security Enthusiast, Security Blogger, Technical Editor, Certified Ethical Hacker, Author at Cybers Guards & w-se. Previously, he worked as a security news reporter.