tildemark

This plugin will completely disable or deactivate XML-RPC on your WordPress installation. This will prevent any brute force attacks to your website using XML-RPC.
By using the plugin, it will remove your ability to post using XML-RPC protocol, which means no more,
<ul>
<li>post ping backs, </li>
<li>remote post from WordPress mobile app, </li>
<li>remote post from windows live writer, </li>
<li>and other applications that requires XML-RPC.</li>
</ul>

Deactivate XML-RPC on WordPress

This plugin will completely disable or deactivates XML-RPC on your WordPress installation. This will prevent any brute force attacks to your website u …

Rob Scott

The XMLRPC Pingback Ping can potentially be used as part of a DDOS attack. 
If you do not need the functionality, this plugin will use core functions to disable it.

Eazy XMLRPC Pingback Disable

This plugin disables the WordPress XMLRPC pingback ping.

Deactivate XML-RPC on WordPress vs Eazy XMLRPC Pingback Disable