Do you need to protect your media assets from unauthorized downloading by 3rd parties? Check out this 'soon to be packaged' package, which enables you to store docs on a secure location so only members (or member groups) are allowed to download after logging in.
Full source code available on Codeplex, no package released yet as there's no way to export a media type using the umbraco packager. Documentation on configuration and installation soon to be released.