Downloading Images.

I've been using Adobe Lightroom for sometime now and I love it but I have found that when I upload a images for clients to view I have noticed that if I do not give them full access to download someone have managed to download images. 

I have found that even though you have not given full access to your images if you right click on your mouse it lets you download any images. Having a platform like Adobe you would have thought that this would be impossible to do but here we are. Any help would be great.