fpoller

Gives the following options for making the WordPress installation more private:
<ul>
<li>Protect content from being viewed to users who hasn’t logged in</li>
<li>Disable all feeds</li>
<li>Only serve uploaded files to logged in users</li>
<li>IP address based exceptions for the above options</li>
</ul>

Private WP suite

Adds option in the admin panel for making your blog (including rss feeds and uploaded files) private.

Dion Hulse

This plugin offers limited support. Please do not expect new features or too many bugfixes. Features may be removed at any time.
Add From Server is designed to help ease the pain of bad web hosts, allowing you to upload files via FTP or SSH and later import them into WordPress.
This plugin is NOT designed to.. 
 * Be used as a replacement for the file uploader 
 * Be used for migration of websites 
 * Re-import your files after moving webhosting 
 * Batch import media
This plugins IS designed to.. 
 * Import files which are larger than your hosting allows to be uploaded. 
 * Import files which are too large for your internet connections upload speed.
WordPress does a better job of file uploads than this plugin, so please consider your needs before you use it.
You may also want to look at using WP-CLI for media import purposes: 
https://developer.wordpress.org/cli/commands/media/import/

Add From Server

Whenever I need to upload media files that are too big to upload directly to WordPress, I FTP them to the server and use this plugin to add them.

Great tool for those big media files you can only ftp to the server

Add From Server is designed to help ease the pain of bad web hosts, allowing you to upload files via FTP or SSH and later import them into WordPress.

Private WP suite vs Add From Server