bozdoz

<a href="https://wordpress.org/plugins/jetpack/" rel="ugc">Jetpack</a> makes it easy to add contact forms to your WordPress site, but you may want a simple way to add a <a href="https://www.google.com/recaptcha/" rel="nofollow ugc">Google reCAPTCHA</a> to prevent spam. This plugin will manipulate the Jetpack <code>[contact-form]</code> shortcode to prepend the Google script, add a button, and parse the response.
This plugin allows both reCAPTCHA v2 and invisible reCAPTCHA (see screenshots and choose whatever works for you!).
Shoot me a question about it on Twitter: <a href="https://www.twitter.com/bozdoz/" rel="nofollow ugc">@bozdoz</a>.
This plugin is open source on <a href="https://github.com/bozdoz/wp-plugin-recaptcha-jetpack" rel="nofollow ugc">GitHub</a>!

reCAPTCHA Jetpack

A simple plugin that adds a Google reCAPTCHA to the Jetpack contact form. Requires the Jetpack plugin.

Pascal CESCATO

Stop XML-RPC Attacks protects your WordPress site from XML-RPC brute force attacks, DDoS attempts, and reconnaissance probes while maintaining compatibility with essential services like Jetpack and WooCommerce.
Features:
<ul>
<li>Three security modes: Full Disable, Guest Disable, or Selective Blocking</li>
<li>Blocks dangerous methods: system.multicall, pingback.ping, and more</li>
<li>Compatible with Jetpack and WooCommerce</li>
<li>Optional user enumeration blocking</li>
<li>Attack logging for monitoring</li>
<li>Zero configuration required – works out of the box</li>
<li>Clean, intuitive admin interface</li>
</ul>

Stop XML-RPC Attacks

Blocks dangerous XML-RPC methods while preserving Jetpack, WooCommerce, and mobile apps compatibility.

reCAPTCHA Jetpack vs Stop XML-RPC Attacks