How to protect download/media

I just had some media stolen so how to I protect my media using the protect download/meadia partion... I can't find the manuel on line and the instruction don't make sense to this new guy ...lol sorry ... so lets say the address of my media is http://www.mysite.com/myarea/mymedia.flv... how do I get the url when ever its viewed to say something else to mask it's location