Block XMLRPC Brute Force Amplification Attacks on WordPress

xmlrpc-brute-protection.php

<?php
/*
Plugin Name: XML-RPC Brute Protection
Description: Disable XML-RPC methods used in brute-force amplification attacks
Author: Keith Solomon
Version: 1.0
License: GPL2
*/

function mmx_remove_xmlrpc_methods($methods) {
	unset($methods['system.multicall']);
	unset($methods['system.listMethods']);
	unset($methods['system.getCapabilities']);

	return $methods;
}

add_filter( 'xmlrpc_methods', 'mmx_remove_xmlrpc_methods');
?>

For future reference.

Rewrite using clousure

add_filter( 'xmlrpc_methods', function( $methods ) {
    unset($methods['system.multicall']);
    unset($methods['system.listMethods']);
    unset($methods['system.getCapabilities']);
    return $methods;
} );