WARNING: If you do not understand what you are doing you WILL really screw up your system. I take no responsibility for this.
Did you ever need to intercept DLL functions that are part of the Windows API? There are many good reasons for doing this; application debugging, process spying, clocking, etc. Even more powerful than function interception is the ability to modify the response of function calls back to the application. This is precisely what DLL Proxying (also known as DLL Hijacking) allows you to do.
In the following tutorial we are going to intercept Mozilla Firefox’s function call to the Windows Socket Library, “wsock32.dll”. The function is called “gethostbyname”. This function is invoked each time Firefox performs a DNS lookup of a domain name. Once this function is intercepted, our proxy DLL will log each URL that Firefox requests, outputting each request to a log file.