Sparanoid

Media Auto Hash Rename will rename any file (specific files can be ignored by file extension) during upload, with unique, low collision hashes. Hash characters and length can be configured for even lower collision rate.
More information please visit my <a href="https://sparanoid.com/work/media-auto-hash-rename/" rel="nofollow ugc">site</a>.
This plugin provides no configuration GUI to make it more easier to maintain with the future WordPress updates.
Currently there’re 3 constants you can configure in your <code>wp-config.php</code>, I recommend WP-CLI for maintaining these constants.
<ul>
<li><code>MAHR_LENGTH</code>: length of the random hashes, (default to <code>8</code>), longer can help reduce collision. Hashes at the length of 8 can be collision-free at the scale of 50,000 images).</li>
<li><code>MAHR_CHARS</code>: Characters used in hashes, default to <code>0123456789abcdefghijklmnopqrstuvwxyz_</code>, You can add more characters like uppercased alphabelts to dramatically reduce the collision without increasing the length of your filenames. But please note that this option can be dangerous if you’re not familer with general URI encoding. So if you don’t know what characters are allowed in a filename, just keep it untouched and use the default option.</li>
<li><code>MAHR_IGNORE</code>: File extensions to be ignored, default to <code>pdf, zip</code>, you can define a comma delimited list of file extensions to bypass renaming process of this plugin. All files that has the file extension you defined in the list will be ignored. Please note that:
<ul>
<li>File extensions must be defined without the leading peroid, for example: <code>'pdf, 7z, bmp'</code> works, <code>'.pdf, .7z, .bmp'</code> does not.</li>
<li>With (<code>'pdf, zip'</code>) or without (<code>'pdf,zip'</code>) space both work.</li>
<li>If you define your own ignore list, default ignore list will be discarded. For example, if you define <code>'7z'</code>, then <code>'pdf, zip'</code> will be processed during upload. You need to reapply these extensions with your own: <code>'7z, pdf, zip'</code>.</li>
<li>If you don’t need to ignore any files by its extension. define an empty array <code>[]</code> (without quotes) to this option: <code>define( 'MAR_IGNORE', [] );</code> to force process PDF and ZIP files.</li>
</ul>
</li>
</ul>

Media Auto Hash Rename

Rename media filename during upload with unique hash.

Fabian

Traffic Limiter is a useful addon for blogs with many media files which can cause high data traffic. 
There are three traffic limits to avoid over traffic costs: daily, weekly and monthly limit. If one of these limits is exceeded downloads will either be redirected to a custom URL or a custom message is displayed. For images you can define a fallback icon which is displayed instead of the message. Additionally a download bandwidth can be set for registered users and guests.
Also included is a statistic system which displays the current traffic consumption and individual file stats to see which media produces the most traffic.
All files are sent to the browser by a PHP script, supporting the most HTTP headers like <code>If-Modified-Since</code> (for caching) and <code>Range</code> (for partial downloads)
If the Apache extension <code>mod_rewrite</code> is installed download links stay the same, if not links to media files are automatically redirected. It is recommended to install <code>mod_rewrite</code>, although this plugin works without this extension.
Note: If you provide lots of downloads or media files you should try my download manager <a href="https://wordpress.org/extend/plugins/wp-filebase/" title="WP-Filebase" rel="ugc">WP-Filebase</a>.

Traffic Limiter

Limits traffic and download bandwidth of media files. Additionally this plugin includes a download statistic system.

Media Auto Hash Rename vs Traffic Limiter