REST API /users/

To enumerate users :

curl -L http://$1/wp-json/wp/v2/users

To prevent this :

add_filter( 'rest_endpoints', function( $endpoints ) {

    if ( isset( $endpoints['/wp/v2/users'] ) ) {
        unset( $endpoints['/wp/v2/users'] );
    }

	if ( isset( $endpoints['/wp/v2/users/(?P<id>[\d]+)'] ) ) {
        unset( $endpoints['/wp/v2/users/(?P<id>[\d]+)'] );
    }

	return $endpoints;

});