Privacy settings not funtional on gallery images

Hello
I am not sure whether i am naif or ignorant of what is happening but i have an issue.
I have node galleries (6.x-2.0-alpha11) module installed and working fine.

I have enabled the security for a gallery (xyz) as private so that only registered users can view the gallery.
How ever the photos inside that gallery can be accessed directly by everyone (anonymous) with the image url.
for ex: galery xyz url is http://www.website.com/node/123
The url for photos (images) inside the gallery is www.website.com/node/124 and so on.
But the actual url of the image will be
http://www.website.com/sites/default/files/imagecache/node-gallery-displ...
(this can be viewed by mouse right click on the image or from the page source)

scenario:
The gallery is not able to be accessed by anonymous user bcas it is set to private (this is fine), but the images inside the gallery can be accessed with the url of the image directly.

My doubt is if we set the gallery as private how can we be able to view/access the images inside the gallery as anonymous user?

Is there something i am missing here?
Please help me on this.