Monday, April 10, 2017

How Proxy Settings in Web Browsers Works?

Normally what a proxy doing is just hiding your identity to the outside world. It can also be used to filter traffic by deep packet inspection. In your enterprise a firewall will do this too. This post is about the proxies we deploy in a server in your LAN which will allow you to access internet via a web browser.

In the 1st capture you can see the normal traffic path to internet from user's PC. What a network administrator does is that he will block all the traffic to internet via an Access List etc and will only allow the proxy server IP to reach out to internet.

So if you hit a ping to a server at internet will be dropped and a trace route will be dropped at 192.168.1.254

So when the LAN user needs to access the internet, network admin will configure proxy settings in your web browser. What he will do actually is he will give the proxy server IP and the port number in advanced settings in web browser. After that the user will be able to browse internet from that web browser only because only those traffic will be directed to the proxy by the PC.

For the internet traffic from the configured web browser will be like in the 2nd capture. The gateway will see they are generating from proxy server it self.

Still pings and trace routes from PC command prompt will be dropped at 192.168.1.254 because those traffic will not be forwarded to the proxy.

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