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.

yehudah

multipie ways to help block xmlrpc attacks.
This plugin have this options:
First Option: 
Log errors and access – to debug plugin errors and access to the xmlrpc file.
The protection options:
<ul>
<li>Disable xmlrpc – disable the file complete with wordpress built in option.</li>
<li>Block login errors ip’s in htaccess – every WRONG login attempt will be blocked inside the htaccess file.</li>
<li>Enable xmlrpc for a specific user – give permission to access the file to pre define user you will choose.</li>
<li>Disable xmlrpc built in functions – xmlrpc have many options and actions to query on your wordpress site, with this option you can choose which option to disable and wich to keep enabled.</li>
</ul>

xmlrpc attacks blocker

multipie ways to help block xmlrpc attacks.

Secure XML-RPC vs xmlrpc attacks blocker