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.

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 …

XML-RPC De-whitespacer vs Deactivate XML-RPC on WordPress