Protect CDN to only server up files if user is Auth - IIS 7
===

We found an issue with our in-house CDN solution.

An Auth user adds photo's or docs to their project.
We upload the files to local driver on the server different from the website application.

    Example: mysite.com [ d:\websites\mysite.com\]  running web-app
    Example: cdn.mysite.com [ e:\cdn\mysite.com\assests\]  storage area

If a Auth user uploads a an image ... then right-clicks on it, the exposed URL 
is:

    http://cdn.mysite.com/assests/30b3bddc-fe1b-4fef-92c0-576bb6e5b487
    /p/347e4ec6-3e36-4ac3-932a-a686d3cffd51/t/347e4ec6-3e36-4ac3-932a-a686d3cffd
    51.jpg

We are using GUID for the Project Folder / User Folder / ImageName.jpg

However, if you copy/paste and send this URL to a friend (Not Auth user), you can access the image/file/etc ... 

How can we protect the CDN to only server up files if user is Auth?

Windows 2008 Server
IIS 7
ASP.NET 4
C# Web app


