perl-booru and other on-the-like programs don't identify themselves for now so hiding images would be enough to defeat those for now, but I guess it's right to do it even harder because that would be temporal. Although nothing lasts forever.

Happy new year everybody btw

EDIT: what I said it's not entirely correct, perl-booru parses the thumbs url and generates with it the full-urls, so maybe something like a script that reads the image instead of delivering it directly. And that script check if it's logged in or not