Disable xmlrpc.php via the .htacess File Print

In your .htaccess file, add this code:

<Files xmlrpc.php>
Order Allow,Deny
Deny from all
</Files>

or 

<Files xmlrpc.php>
order deny,allow
deny from all
allow from xxx.xxx.xxx.xxx
</Files>

Replacing the xxx.xxx.xxx.xxx with the IP of the service you wish to have access your xmlrpc.php file.

or 

Search for "Disable XML-RPC" and install the Disable XML-RPC plugin.

Make sure you make a copy of the old file before you do so, just in case you run into any issues.