The default configuration of the LightRocket Media Manager platform features a front and back end.
The back end is only accessible to registered contributors and admins. The front end is usually an open online space where members of the public may browse files that have been 'published' and for which access has not been restricted.
It's important to note that for all files published to the front end of your system though they may be visible, NONE will be downloadable without the user being logged in and/or having appropriate permissions.
However, it is possible to restrict access to even the front end of your platform by creating a gateway landing page where visitors would be required to either register or log in before proceeding to your site.