I remember seeing this a while ago here in the admin forum, but since I can't view that now, thought I'd ask. I know some people who have sites on our site network and people are linking to their images (car blueprints) and stealing bandwidth. I know it involves the rewrite engine. I'd like to possible block all .gif and .jpg files from being linked and then replacing the images with a 'You are linking to a file on our servers and stealing our bandwidth. Please cease and desist." image.
Cheers,
Dan