Max Cutler

Uses PHP’s output buffering to buffer XML-RPC responses and strip superfluous whitespace.
Plugins, themes, and any other files executed during the WordPress load process can unintentionally emit whitespace, 
such as by including a newline character after an explicit closing “?>” PHP tag instead of letting PHP auto-close the 
file.

XML-RPC De-whitespacer

Removes leading and trailing whitespace from XML-RPC responses that can break some XML-RPC clients.

brainvireinfo

You can now disable XML-RPC to avoid Brute force attack for given IPs or can even enable access for some IPs. XML-RPC on WordPress is actually an API that gives developers who build mobile apps, desktop apps and other services, the ability to talk to a WordPress site. The XML-RPC API that WordPress provides gives developers, a way to write applications (for you) that can do many of the things that you can do when logged into WordPress via the web interface.
<h4>Features</h4>
Block XML-RPC by following way.
<ul>
<li>Disable pingback.ping, pingback.extensions.getPingbacks and Unset X-Pingback from HTTP headers, that will block bots to access specified method.</li>
<li>Disable/Block XML-RPC for all users.</li>
</ul>

Manage XML-RPC

Enable/Disable XML-RPC for all or based on IP list, also you can control pingback and Unset X-Pingback from HTTP headers.

XML-RPC De-whitespacer vs Manage XML-RPC