isaacchapman

The Htaccess Secure Files plugin can only be activated on Apache web servers with mod_rewrite enabled, and will automatically raise an error upon activation if this is not the case.
The Htaccess Secure Files plugin allows for setting files to be accessible only to visitors who have a specified IP address or <a title="WordPress role or capbility" href="https://codex.wordpress.org/Roles_and_Capabilities" rel="nofollow ugc">WordPress role or capability</a>. By using <a title=".htaccess files" href="http://en.wikipedia.org/wiki/Htaccess" rel="nofollow ugc">.htaccess files</a> to secure the content instead of a separate directory outside the web root, WordPress’s native media library functionality can be used to upload secure files and link to them from within the visual editor.
By default all built-in WordPress roles will be allowed to access content that is marked as secure. The Settings -> Secure Files admin screen controls which roles, capabilities, and IP addresses are allowed to view or download secured files. If a custom role or capability is desired, there are several <a title="WordPress plugins" href="https://wordpress.org/extend/plugins/search.php?q=roles+capabilities" rel="ugc">WordPress plugins</a> capable of creating and editing roles and capabilities.
Any visitor that matches any selected role, capability, or IP address will be allowed to access secured files.
This plugin works by creating a .htaccess files in the directory of each secured file. If you manually edit the .htaccess file and it becomes corrupt (a 500 Internal Server Error is the most likely symptom), I recommend deleting the .htaccess file and then edit and save each secured item in the media library.

Htaccess Secure Files

Allows securing files in WP's media library to be only accessible to users with specific roles, capabilities, or IP addresses.

Niteo

Spider Blocker blocks most common bots that consume bandwidth and slow down your blog. 
It accomplishes this by using .htaccess file to minimize impact on your website. It’s hidden from external scanners.
Spider Blocker is specifically designed for Apache servers with mod_rewrite enabled, allowing you to effortlessly safeguard your website from the most prevalent bots that hamper performance and drain resources.
<h4>Plugin Features</h4>
<ul>
<li>Block Unlimited bots from viewing your site</li>
<li>Easy Export/Import rules (comes with most common list of bots)</li>
<li>Zero Footprint</li>
</ul>

Spider Blocker

Does what it promises to do. No more bad bots to my WP blog :)

Perfect!

SpiderBlocker will block most common bots that consume bandwidth and slow down your blog.

Htaccess Secure Files vs Spider Blocker