This technique is called "hotlink protection". But it can also be used for simple protection against downloading. It is based on checking the Referer header and is described in the mod_rewrite documentation .
Of course, if you wish, you can still download the file by substituting your own Referer header, since this header is sent by the user. Or download using the plugin. But from a simple download link this method protects.
In .htaccess you need to add a rule like this:
RewriteCond "%{HTTP_REFERER}" "!www.example.com" [NC] RewriteRule "\.(mp4|avi|mov)$" "-" [F,NC]