What's the best way to protect Amazon S3 videos

Quick question for the amazing WPMUDev Wordpress Ninjas... :wink:

I run a website with a private membership area, called "Labo Marketing".

On that membership area, I host some videos on Amazon S3...

My question is : how can I best protect these videos so my customers can't download and share them (i.e. so they can ONLY be accessed within the membership area) ?

What are the best ways to do that ?

Thanks a lot in advance for your suggestions and valuable input !