How to protect Digital downloads Folders ?

How to make the folder containing my products (downloadable videos) more secure ?

Also my videos are not 8mo files !
But around 300-500 Mo Files !!
I suppose I have to FTP them directly into a folder ?
Which folder ?

What do you suggest ?

Plugins such as S2Member have HUGE security features regarding digital downloads ...
Could you implement something similar ?

Thank you