What causes an IP address to leak?

What is an IP address leak?

An IP address leak is the accidental exposure of your real IP address to third parties, including websites, internet service providers (ISPs), and advertisers, even though you're using a VPN to hide it. These parties should see the IP address displayed by your privacy tool, but instead, your real IP address is exposed.

Your IP address is the unique numerical label that is assigned to your device when it connects to a network. You can find your IP address using an online lookup tool, which shows what information is currently visible to websites and other online services. Like your home address or phone number, different types of IP addresses can be used to glean information about you, such as your network and approximate location. To protect this information, many people use VPNs or other privacy tools to mask their real IP addresses.

What is an IP address leak?

An IP address leak is the accidental exposure of your real IP address to third parties, including websites, internet service providers (ISPs), and advertisers, even though you're using a VPN to hide it. These parties should see the IP address displayed by your privacy tool, but instead, your real IP address is exposed.

Your IP address is the unique numerical label that is assigned to your device when it connects to a network. You can find your IP address using an online lookup tool, which shows what information is currently visible to websites and other online services. Like your home address or phone number, different types of IP addresses can be used to glean information about you, such as your network and approximate location. To protect this information, many people use VPNs or other privacy tools to mask their real IP addresses.

What are the risks of an IP address leak?

Knowing what someone can do with your IP address goes beyond a simple privacy concern. Third parties that gain access to your IP address may be able to see your online activity, location, network, and browsing history.

• ISP tracking. Your ISP may be able to see and document your browsing history if your IP address leaks. Depending on your local laws, the collected data could be used to monitor the websites and services you access.
• Government surveillance. In some regions, government agencies may monitor internet traffic. If your IP address is exposed, associating online activity with your specific connection becomes easier.
• Targeted cyberattacks. While an IP address on its own is not enough to compromise your device, you could be prone to hacking attempts if someone has your IP address. They may use information gained from the leak, such as location information, to initiate phishing or malware campaigns. They can also perform port scans, identify potentially vulnerable services, and attempt to exploit weaknesses in your security, which they deduce from your IP address.
• Doxing and personal identification. You can still be tracked with a VPN if an IP address leak is actively occurring. A leak does not reveal your home address, but it can be used alongside social media, data breaches, and your approximate location to narrow down your identity.

Common causes of IP address leaks

While VPNs and other privacy tools are designed to hide your actual IP address, incidents such as technical issues, software changes, and network behaviors can expose it. Most commonly, IP leaks are caused by DNS, WebRTC, or IPv6 leaks, as well as VPN misconfigurations, VPNs that disconnect unexpectedly, transparent DNS proxies, and some specific features of your operating system.

DNS leaks

A DNS, or Domain Name System, translates human-readable website names (such as “google.com”) and their machine-readable, numerical IP addresses. When your device sends a DNS request outside of your VPN tunnel, rather than through the VPN’s DNS server, your ISP may be able to see your browsing activity. 

DNS leaks can happen for several reasons. One common cause is a misconfigured VPN, which is not set up to route your DNS requests through an encrypted tunnel. Some VPNs may use third-party providers instead of operating their own DNS, which creates another step in the chain and increases the risk of a leak. In some cases, an operating system’s network settings may override the DNS configuration of your VPN.

DNS leaks are not the same as DNS spoofing. Leaks expose your requests outside the VPN tunnel. Spoofing tricks your device into believing it’s connecting to a secure site, when really it’s being diverted to a malicious site.

WebRTC leaks

WebRTC (Web Real-Time Communication) is a browser-based technology that allows you to use real-time audio, video, and data sharing technology. WebRTC can leak your real IP address, even if you are connected to a VPN, by establishing a peer-to-peer connection through a STUN server, which determines your network configuration. This connection grants access to browser APIs. If your VPN does not properly block or mask this interaction, your real IP address could come through.

Web browsers that have WebRTC enabled by default, such as Google Chrome and other Chromium-based browsers (like Microsoft Edge and Opera), are often what cause an IP address to leak. WebRTC operates at the browser level, which is why VPNs on the network level may not keep your IP address private if your privacy tools are not properly configured.

IPv6 leaks

TCP/IP (Transmission Control Protocol/Internet Protocol) is the foundational architecture that governs internet communication, and within it, IPv4 and IPv6 are two types of address systems. They provide unique IP addresses. IPv4 is older, and IPv6 was designed to succeed it, but many IPv4 IP addresses remain in use. Some VPNs only tunnel IPv4 traffic, while IPv6 traffic is unprotected. When a website or service uses IPv6, the request may bypass the VPN tunnel entirely, which exposes the user's real IPv6 address.

IPv6 leak protection requires either using a VPN that fully supports IPv6 traffic or disabling IPv6 connections, which will cause all traffic to remain within the VPN’s encrypted tunnel.

Misconfigured VPN

Improper VPN setup is one of the leading causes of IP leaks. If your DNS configuration is set up incorrectly, the system may use your ISP’s default DNS servers instead of the VPN’s protected ones. Split tunneling misconfigurations work similarly, which creates exposure if some applications or websites are accidentally excluded from the VPN’s tunnel. 

Due to how a VPN works with its encrypted tunnel, the failure point comes from traffic that is accidentally excluded from the VPN. If you frequently switch networks (like, from home Wi-Fi to public Wi-Fi or mobile hotspots), you are especially vulnerable. Each network change can alter the system routing rules.

VPN disconnections and network disruptions

If you’re connected to the internet and your VPN connection drops unexpectedly, there may be a brief window in which your real IP address is exposed. Unstable Wi-Fi connections can cause a drop, as can switching between networks. Sometimes, your VPN service might experience an internal issue that causes a temporary drop.

To prevent an IP leak in the event of a disruption, some VPNs include a kill switch feature. This kill switch automatically blocks internet traffic until the VPN is active again.

Transparent DNS proxies

In some instances, your ISP might be what causes your IP address to leak. Some ISPs use transparent DNS proxies that intercept your outgoing DNS queries and redirect them to the ISP's own server. Even if you have a different DNS configuration, your ISP’s DNS proxies can override your VPN settings and cause leaks.

In many cases, DNS leaks happen because rerouting occurs without your knowledge. Rerouting operates at the network level, so you may have no clear evidence that traffic is not being routed according to your VPN’s DNS settings.

Operating system features

Your device’s operating system can contribute to IP address leaks. On Windows, one well-known example is Smart Multi-Homed Name Resolution, which sends DNS queries to multiple available network interfaces at the same time. Each of these queries is its own risk, which may result in information being sent outside the VPN tunnel. 

Teredo is another relevant example. Teredo is a transition technology that allows IPv6 traffic to be transmitted over IPv4 networks, which means that your VPN may not capture this traffic. Other operating systems may experience similar issues, though they may differ based on the infrastructure.

How to test for IP leaks

If you’re unsure whether your IP address has been leaked, you can track your IP address by using a leak testing tool. These tools can reveal whether your real IP address, DNS requests, or WebRTC information are being exposed, even if you already have a VPN. 

You can check if your VPN is working by connecting to your VPN first. Then, visit a testing website (such as ipleak.net, browserleaks.com, or nordvpn.com/dns-leak-test/) to conduct a DNS leak test. Compare the displayed IP with your real IP, paying attention to any IP address mismatches, which DNS servers appear in the results, and whether your browser is revealing your real IP address through WebRTC. 

How to fix and prevent IP address leaks

If a leak test reveals a problem, the next question is what causes your IP address to leak despite your VPN, and how you fix the leak. The answer depends on the cause of the leak, but in many cases, changing your settings or choosing the right tools can reduce the risk of exposing your real IP address.

Use a VPN with built-in leak protection

The most effective way to fix and prevent IP leaks is to choose a VPN that offers a kill switch and built-in protection against DNS and IPv6 leaks. To understand how VPNs protect you from data leaks, look at NordVPN's built-in features: secure servers, automatic kill switches, and IPv6 leak protection. Try NordVPN to see the difference that multi-layered  IP protection can make.

Enable a kill switch

A kill switch is a VPN feature that can cut internet access if the VPN connection drops. By disconnecting from the internet, your device can no longer share its real IP address while the VPN is down. You can enable this feature in your VPN settings as long as your VPN includes a kill switch function. 

Disable WebRTC in your browser

WebRTC is a browser-level vulnerability for your IP address. Chromium-based web browsers, such as Google Chrome, Microsoft Edge, and Opera, do not contain a built-in setting to completely disable WebRTC. You can still protect your information by using browser extensions that include leak protection.

In Mozilla Firefox, the browser settings include some options to limit WebRTC’s ability to expose your IP address. However, disabling or restricting WebRTC can affect services that rely on real-time communication. You may not experience the same quality in video conferencing or file sharing. Test these services after making changes to make sure they continue to function properly.

Configure DNS settings manually

Instead of relying on your internet provider’s default DNS server, you can configure your own DNS settings. Consider specifying a custom DNS server (like your VPN provider’s DNS) at the device or network level, depending on your operating system. You can also use DNS-over-HTTPS (DoH) and DNS-over-TLS (DoT) for additional security. These technologies encrypt DNS queries while they travel between your device and the DNS resolver, which makes intercepting or modifying the information more difficult. 

Run regular IP leak tests

Even if you have all your privacy settings adjusted and your VPN up and running, new leak risks can develop over time due to software updates, network changes, and other factors you can’t predict. Running periodic testing should be a part of your regular routine, especially after changing networks, updating your VPN software, or modifying system settings.

Occasional testing only takes a few minutes. If you can identify what causes an IP address to leak on your specific network settings, frequent testing allows you to fix it early, before your real IP address is exposed further.

What to do if your IP address is leaked

If you’ve discovered a data leak, taking prompt action can help you restore your privacy and minimize the risk of future exposure.

• Disconnect from the internet: An internet connection can continue to expose your real IP address for as long as you’re connected. Temporarily disconnect while you investigate.
• Reconnect through a VPN: Reconnect through a VPN to get a fake IP address, then verify that your VPN is properly configured with DNS leak protection, IPv6 leak protection, and a kill switch.
• Run a leak test: After making changes, perform IP, DNS, and WebRTC leak tests to confirm that the issue has been resolved.

An IP address leak doesn’t necessarily mean that you need to change your IP address. However, if you’re experiencing doxing or network attacks, getting a new IP address could be a worthwhile next step.