Good solution for protecting image files in folder

[eluser]esset[/eluser]
So let's say I have a folder in my server-root called /images/.

Now I want to protect all images in this folder (and subfolder) from direct access (like www.mydomain.com/images/001/image.jpg).

But I still want my server and/or PHP files to be able to access this folder (and subfolders/images).


Anyone got a good solution for this?

Thanks