Disables the XML-RPC API in WordPress 3.5+, which is enabled by default.
Pretty simply, this plugin uses the built-in WordPress filter "xmlrpc_enabled" to disable the XML-RPC API on a WordPress site running 3.5 or above.
Beginning in 3.5, XML-RPC is enabled by default. Additionally, the option to disable/enable XML-RPC was removed. For various reasons, site owners may wish to disable this functionality. This plugin provides an easy way to do so.
Step 1: Install it
Install this plugin by navigating Plugins -> Add New within your Admin dashboard, then searching for ' Disable XML-RPC ', then click Install, then activate.
Alternatively you can head over here, download the plugin and then upload and extract it to your WordPress plugins folder.
Step 2: Use it
Use the plugin as shown in the below screenshots:
Reference
Read more here.