How do you detect if someone is using a VPN or not?
How do you detect if someone is using a VPN or not?
You can't check that. All you can do is verify source IP of connection to a list of known VPN gateways, which essentially is ever-incomplete. Big VPN vendors constantly spin new servers, there are probably tens of thousands of non-public VPNs running at homes, universities and companies. You can't catch them all.
It depends where you are observing from.
If you are capturing packets (“man in the middle”) then the pattern of packets, source and destination ports will be the thing you look for. Many VPN’s use well known ports of protocols that can be observed outside the encrypted envelope. for example UDP port 1194 is usually open VPN traffic. This is called traffic analysis.
If you are a service operator trying to determine if a user is connecting via a VPN it’s a bit more complex. Their traffic will appear to originate from the VPN exit node. Depending on the VPN in use that may or may not give it away. Many public VPN services can be mapped if you have enough sample data (Netflix does this). However a private VPN such as the one I use to connect back to my home router is much harder to detect becasue the traffic appears to originate from my home internet connection.
Some operating systems (certain Windows versions) can be provoked into sending DNS queries outside the VPN, by requesting a unique host address and logging the resulting DNS access you may be able to determine the true IP.
There are also commercial services that will tell you if a connection is a VPN - google “VPN detection“ and you’ll find several.
Yes, Wireshark is the tool to use to see if someone is connect6ing to your network from a “strange” IP address (using a VPN) - or to find out other things about your traffic, but the question is WHY?? Why do you care? There are two kinds of VPN The original one used by corporations to Specifically allow the user to log into a corporate network from outside the network superstructure - Which is something that you would be given credentials or a specific client to use - and something your network security set up specifically to allow you to connect.
Then there is the newer version advertised as a service for internet users (While it actually uses the same methods, I (as an IT professional) truly wish they had used a different name. What the internet VPN is used for is “hiding” your actual IP address. This is very useful if your country limits where your ISP allows you to go - The VPN fools the internet into thinking you are somewhere else. This is also handy if you are doing things that you believe your internet provider would “ban” you for doing, and yes - if you truly believe that the internet is following you to target advertising based on your activity (It is) a VPN service will allow you to “hide” from some of that activity.
The thing is - If you have a corporate network that has a VPN, you would have the tools to know who is connecting, and you would not give out your VPN client to anyone that you are not doing business with. If you just have a website or other PUBLIC FACING internet server - you should feel honored that someone who’s country has blocked your website, feels strongly enough about your site that they would go through hoops (and probably spend money on the service) to reach your site.
Now - If I were a “script kiddie” hacker who just wanted to attempt to do damage (once again - to your Public facing server) I would use a VPN to cover my tracks, as if you were to be able to find out that I did attack, you won’t see my true IP address.
THat is all a VPN does - it hides your IP address or allows you to connect to a corporate network (with permission).
Hope that helps.
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