The WordPress XML-RPC API has been under attack for many years now. Back in August 2014, WordPress released version 3.9.2, fixing a possible denial of service issue in PHP’s XML processing. There are brute-force amplification attacks, reported by Sucuri, and so on. So, how do you protect WordPress from these xmlrpc.php attacks, but still being able to use (some of) its functionality like Jetpack? This post gives you some insight.
WordPress xmlprc.php DDoS and brute-force attacks. How to identify, block, mitigate and leverage these xmlrpc.php scans, brute-force, and user enumeration attacks on WordPress sites… Secure WordPress xmlprc.php interface and reduce service disruption.