Eric Mann

Rather than sending usernames and passwords in plain text with every request, we’re going to use a set of public/secret keys to hash data and authenticate instead.
On your WordPress profile, you will see a new “Remote Publishing Permissions” section listing out the applications that have permission to publish, along with their public and secret keys.
New applications can be added whenever you want. You can also change the names of applications, or revoke publishing permission by deleting them.
<h3>Additional Information</h3>
Lock graphic designed by Scott Lewis from the thenounproject.com

Secure XML-RPC

More secure wrapper for the WordPress XML-RPC interface.

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.

Secure XML-RPC vs Eazy XMLRPC Pingback Disable