We have assessed, using numerous instances, the benefits of REST API and how it is progressing, and we have also looked over the security concerns that might be bothering you. In this regard, we will look over the practical method to disable the JSON REST API in WordPress.
Some website owners might not be using all the features provided by the API, and if they are skeptical about the security concerns that revolve around REST, and you would like to secure themself from a DDoS attack, then similarly to disabling Extensible Markup Language-Remote Procedure Call Protocol (XML-RPC), you could disable the REST API.
To disable the JSON REST API on your WordPress website, you will have to add a piece of code within the functions.php file of your theme files.
add_filter('json_enabled', '__return_false');
add_filter('json_jsonp_enabled', '__return_false');
The code piece above will make use of the available built-in filters, which will then disable the JSON and JSONP APIs...