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.

Scott Reilly

Prevent virtual directory listing services from listing the contents of directories, and/or show a page in place of a directory’s listing.
The Apache web server can be configured to automatically display the listings of the contents of a web site’s file directory if no index file (i.e. index.html or index.php) is present. This can expose files and information to visitors. Of course the web server could be configured to not do this (the recommended approach), but sometimes you don’t have permission (you’re on a shared host), the know-how, or you want to selectively disallow virtual directory listings. That’s where this plugin can help.
If you want to test if your site has virtual directory listings enabled, try visiting http://www.YOURSITE.com/wp-includes (obviously, change the domain to match your own). If you see a listing of PHP files then virtual directory listing is enabled for your site.
This plugin can prevent visitors from seeing the contents of certain (or all) directories on your site (assuming your web server generates virtual directory listings). It also allows you to use a WordPress page as the index for a directory
By default, the following directories are protected:
<ul>
<li>wp-includes/</li>
<li>wp-content/</li>
<li>wp-content/plugins/</li>
<li>wp-content/themes/</li>
</ul>
It does NOT protect any other directory by default. You can change this via the plugin’s admin settings page.
TIP: When this plugin is activated (and more specifically, ater the permalink structure is updated as per the instructions below), WordPress will generate the themed 404 – Not Found page. If you were to create a Page with the same name as one of the directories being disabled (i.e. ‘wp-includes’ or ‘wp-content’) then that page will be displayed instead of the 404 error message. If you want to display a page for the ‘plugins’ and ‘themes’ directory, you must create them as children pages of a ‘wp-content’ page.
NOTE: This plugin only works for the Apache web server.
Links: <a href="http://coffee2code.com/wp-plugins/disable-directory-listings/" rel="nofollow ugc">Plugin Homepage</a> | <a href="http://coffee2code.com" rel="nofollow ugc">Author Homepage</a>

Disable Directory Listings

Prevent virtual directory listing services from listing the contents of directories, and/or show a page in place of a directory's listing.

Spider Blocker vs Disable Directory Listings