Unauthorized Access

[Anne]

What would be the point of having required registration to view pics, if all one has to do is right click on a thumbnail (or view source) and erase the "thumb_" part of the URL? Is there any way around this?

[Aditya Mooley]

That is why it is mod and not a core feature. 
Anyways if you put your pictures on the web, they will be accessible. You can only make it difficult.

[Hein Traag]

The only foolproof way is not putting your pictures online  :-\\

You have to accept that no matter how difficult you make it for unauthorized users to view the full size pics they will always find a way around your defences.

[Tranz]

If you can edit the .htaccess file, you can prevent direct access to files. So if someone tries to access an image by using its URL, you can redirect them elsewhere. The code is used along with the hotlink protection code.