Image & video - antileech?

I’ve recently come into an issue with running antileech (htaccess) but I can’t get it to cooperate:

RewriteEngine on RewriteCond %{HTTP_REFERER} !^$ RewriteCond %{HTTP_REFERER} !^ [NC] RewriteRule [^/]+.(wmv)$ - [F,NC]
I attempted that but then in testing through a few other sites that are pulling the WMV’s, it’s still possible to pull the files. (browser’s cache, history, and cookies have all been cleared).