[Angel-Wings]

Hmmm - can't this be done already with htaccess ?

Something like:

<FilesMatch "attachment\.php">
RewriteCond %{HTTP_REFERRER} !^http://(www\.)?example.com(/)?.*$ [NC]
RewriteRule .*\.*$ - [F,NC]
</FilesMatch>

And when using the filesystem as storage:

<LocationMatch "/uploads">
RewriteCond %{HTTP_REFERRER} !^http://(www\.)?example.com(/)?.*$ [NC]
RewriteRule .*\.*$ - [F,NC]
</LocationMatch>

Or is there any difference like some additional check ? Reading the addon, if I understand it right you parse HTTP_REFERRER too via PHP, doing it directly via the Server is maybe less portable, but maybe also faster that PHP doesn't need to be called everytime.