How to Know if Someone is Using a VPN (Tested)

Online privacy is permanent and so is using a VPN. A VPN service helps in hiding your original IP address by encrypting your internet traffic and routing it through its own dedicated servers. Thus, helping us achieve full anonymity. Although, many cybercriminals use VPNs to perform malicious cyberattacks, and therefore, it is essential to determine “How to know if someone is using a VPN?”

Let’s find out!

How to Know if Someone is Using a VPN?

So, if you are trying to find out who is using a VPN connection, you can simply do it by; investigating if all data that is being sent is allotted to a single IP address or has any DNS leaks, or that particular connection is unstable regarding geo locations or is using a blacklisted IP address. 

Although, it is not easy as it seems because every single VPN company is nowadays more focused on improving its technology to provide its customer with detection-less VPN service. So, if you want to get more details on the topic, read on.

Ways to Detect a VPN Connection:

  • Check if the IP address is consistent:

So, VPN works by hiding your original IP address and camouflaging it with its own, and it is a very foolproof tactic unless the VPN provider is allotting only a single IP address to all. This method is also used by famous streaming services like Netflix and HULU, which helps them to block incoming VPN connections.

So, if anyhow you detect the same IP address everywhere and every time, possibly someone is using a VPN connection.

  • Check if a bunch of encrypted data is moving to an unknown location:

VPN encrypts the traffic so that an ISP or government entity is unable to spy.

Thus, if a bunch of encrypted data is moving to an unknown location, then you can be assured that a VPN connection is being actively used.

  • Check for DNS leaks:

DNS leaks usually occur when your DNS request travels to your ISP instead of your VPN provider. For instance, a DNS works by translating your domain names to IP addresses, but when a user uses a VPN server, these DNS queries travel through the VPN servers, not your ISP.

Although, if your VPN is faulty and leaky, it allows the DNS query to travel straight through your ISP instead, causing DNS leaks. Thus, leaving the user vulnerable to VPN detection. Additionally, rDNS goes a step further and links an IP address to a hostname, that may identify the IP owner.

  •  Check Port numbers:

Some VPN protocols use specific port numbers to establish a VPN connection. For example; OpenVPN (UDP) uses port 1994, OpenVPN (TCP) uses 443.

Therefore, if a VPN connection uses a specific port number, then it is very much possible to detect a VPN connection.

  • Use Deep packet Inspection method:

This is the most advanced method that can be used to track if someone is using a VPN. The Deep Packet Inspection method inspects the structure of each passing data packet, and it is mainly used to block malware or spam. But some government entities like China use it to block VPN connections too.

  • Look for any unstable geo locations:

This is something that can help you instantly track down a VPN user. Usually, while we use a VPN server, it changes our real location to a VPN-based location. For example; If you are in the USA and use a VPN service, you can change your virtual location to Germany.

For instance, if a user opens up an online account from his regional location, and then switches location using a VPN, the ISP can instantly figure out that the user is on a VPN connection.

Or, if a user has accessed a particular website, and then decides to turn on a VPN connection, again ISP can instantly know that the user is using a VPN.

  • Check if numerous accounts are created using a single IP address:

Usually, every website has its own IP address, but if someone is using a VPN service, then only one IP address is being displayed throughout the account creation process. And if a user creates “n” number of accounts with the same IP address, then it is a clear indication of an active VPN connection.

  • Determining blacklisted IP address:

There are many IP addresses online that are blacklisted, and usually, public VPN servers tend to buy these IP addresses. Therefore, it becomes very easy for an ISP to just scan those IPs and block them.

Although, many premium VPN companies tend to use unique and secure IP addresses that are not blacklisted and are hard to detect.

  • Check for WebRTC leaks:

Web Real-time Communication (WebRTC) allows users to access content without plugins and is often used for web-based software. 

Although a VPN user can expose IP addresses to the website, they visit by using JavaScript.

  • Check for inconsistency in OS and Fingerprint Data:

Operating systems create packets with specific values, for example, Windows sets their default packet TTL to 128, while Linux sets it to 64. Therefore, TTL(Time-to-live) is a visible part of a captured packet, and one can easily determine from what OS it is created.

Thus, if you have a perfect guess of the OS your target uses, then it is very much easier to know if that user is on a VPN or not. For example; if you know your target is using macOS and the packets you received belonged to Windows, then it is completely transparent that a VPN connection is being used.

  • Check for any drop in connection:

So, this is the easiest way to track down any VPN connection. If, for instance, a user is on an active VPN connection and suddenly it drops out, then the user is instantly vulnerable to getting detected for a VPN connection.

Therefore, I recommend using a VPN with the Kill Switch feature if you are a VPN user because a Kill switch feature will instantly kill your network connection if your VPN connection goes down, to ensure zero privacy breaches.

Final Remarks:

We all crave privacy in this online world and it is very essential. So, we all should start using a VPN service to keep our internet traffic encrypted and secured from the eyes of our ISPs.

Although, with the increase of VPN services, hackers have started using VPN as their shield, thus leaving many cyberattacks traceless. Therefore, proper ways should be implemented to know if someone is using a VPN. 

Note: The above methods will only work if you have ample knowledge about the same. Also, it is only possible when you stay connected to your ISP for expert help, because most VPN providers are enhancing their security protocols that restrict any kind of VPN detection.