Protecting unauthenticated users from downloading .swf files

Hi

I have in the past had succes with protecting pdf-files from download by
unauthenticated users by adding an application extension in IIS and mapping
pdf.files to be served by the aspnet-process.

I am currently faced with the same challenge - just for swf-files (shockwave
flash). I need only authenticated users to be able to access them.

However - when I make aspnet_isapi.dll handle swf-files, they are not shown
in the browser.

I have no idea why this is happening.

The site runs on a 2003-server and I use Asp.net 2.0, and the site otherwise
runs just fine.

Thanks in advance

Klaus