Uncovering How My LAN IP Was Revealed

[RedX]

I went to one of those websites that look up your WAN IP address, and they gave it correctly, but they also gave me my LAN IP address (192.168.xxx.xxx).

How do they know my LAN IP address? I thought that those outside your LAN only see the public IP address of your router, and only your router knows your LAN IP?

Did the router give that information up?

 

[Rogerio]

Your browser sent the address, and many other parameters like you OS, etc

 

[RedX]

Your browser sent the address, and many other parameters like you OS, etc

I thought the only purpose of my browser is to render and request HTML. I thought internet exchanges were at the application level, and not the operating system level, so why do servers need to know my OS?

 

[lostinxlation]

That's strange. IP packet has only one field for sender's address which carries global IP address after passing your router(after NAT). There shouldn't be any way for outsiders to know your private IP address.

 

[RedX]

That's strange. IP packet has only one field for sender's address which carries global IP address after passing your router(after NAT). There shouldn't be any way for outsiders to know your private IP address.

Well, the website is here:

http://ip-lookup.net/

That's what I thought to, that there is no way, since they only see my global IP address. But maybe it's because you have to click on something for it to tell you your LAN, and by clicking on something, you are sending that information. That's probably it.

 

[lostinxlation]

I clicked on the "LAN IP address", and it kept trying, but has never returned my private IP address. I highly doubt there is any standard way to obtain the private address, but might be possible depending on the setup ?

 

[RedX]

I clicked on the "LAN IP address", and it kept trying, but has never returned my private IP address. I highly doubt there is any standard way to obtain the private address, but might be possible depending on the setup ?

Yeah, it shows my private address correctly when I click on "LAN IP Address". But maybe your router is different. Whenever you click on something, anything goes, your computer can be instructed to send whatever information, so maybe that's how it got my LAN IP address.

 

[lostinxlation]

I'm under the impression the setup of my browser blocked some program to execute to obtain private address. Maybe you can change the security level or disable some functions of your browser to see what will happen.

 

[Rogerio]

I thought the only purpose of my browser is to render and request HTML. I thought internet exchanges were at the application level, and not the operating system level, so why do servers need to know my OS?

The browser sends information about itself and the host (version, OS, release, user, etc...)

That's strange. IP packet has only one field for sender's address which carries global IP address after passing your router(after NAT). There shouldn't be any way for outsiders to know your private IP address.

The info goes inside the payload (data field)

 

[waht]

The website LAN feature attempts to run a java app to retrieve your LAN. But it didn't have enough privileges to access that information.

If anyone is still seeing your LAN, try stepping up the security bar in your browser couple of notches higher.