Anonymizer Proxies basically come in two flavors, web based proxies and application based proxies. The web based proxies (PHProxy, Glype, etc.) grab the content of a web page and basically rewrite the entire page producing the end result to the user. The ip address the web server gets is that of the host which is running the web based proxy thereby hiding the real ip address of the user.

   Application based proxies (JonDo, UltraSurf, etc), however, require a user to download an executable file to their computer and install it. The user then starts it up and reconfigures their web browser to use it. So, the ip address of the user is now the the ip address of the application proxy network that the browser is connected to. Again, the real ip of the user is hidden from the world.

   However, with a little ingenuity, and a bit of Java knowledge it is possible to have the user “phone home” his or her real ip address. Below is an example:

   Of course, the user’s web browser must have Java enabled for the applet to phone home but most proxy users just use the default settings of their browser which has Java enabled out of the box.

   So, it is actually possible to get the real ip address of users believing they are safe behind an anonymizer proxy.