nkyre

WordPress upload file names can be quite predictable sometimes, especially if uploading from the same camera – DKIM1004 comes after DKIM1003. If not all of the content on your site is public, this can be a problem as people can snoop on your media folder by guessing file names.
This plugin prepends a short 8 character hash to the beginning of every uploaded file. For example, DKIM1004.jpg turns into 8df8078e-DKIM1004.jpg. The hash is not cryptographically secure and just makes it a bit more difficult to guess file names.
The plugin works on all upload file types and all sizes of a given image get the same prefix.

Media File Name Guess Preventer

Prepend a random string to media file uploads to prevent file name guessing.

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.

Media File Name Guess Preventer vs Add From Server