Hot-linking files such as images and media (mp3, wma etc..) is where another website uses source code to post your media on thier page. This uses your bandwidth and the other site gets credit for this.
This snippet of code will prevent anyone but your domain to view or access your media. If others are hosting images that are yours they will simply have the big red x.
There are 4 variants of this code, experiement with them to find the one that works for you.
To implement this you will need to create a .htaccess file in the stored directory. If your images are in /web/images then you will need to post this .htaccess file in the images directory to prevent hotlinking there.
I don't know either but you could use another method which is actually more secure for your whole site, why not protect your source code by using encryption and also use one of those 'no right click' scripts. There are some no right click scripts that can be passed by simply left-clicking and quickly right-clicking after it, so be careful as not to pick a duff script This way all your content is protected. not just your images etc because it stops them right clicking and selecting 'save target as' or viewing your source for the file location.
mod_rewrite is no longer full prove and I can tell you why..
I found people are using XML (.xml) to get thourgh mod_rewrite.
An example is an mpg file with mod_rewrite hotlinking protection. If request is not coming from your web page, apache sends error 302 and attempt to redirect, somehow, since it is .xml, with an embedded Windows Media Player, the client was not redirected to a hotlink page.
Instead another request was made to the server by the embedded player for the mpg file. At this time there is no refferal information. Then client is able to download and play the mpg file on the stealer web page and therefore stealing your content and bandwidth.
This http log might better explain what is going on...