itthinx

Activate and the Captcha will appear on the affiliate registration form when the <a href="https://wordpress.org/plugins/captcha/" rel="ugc">Captcha</a> plugin is activated.
Requirements:
<ul>
<li><a href="https://wordpress.org/plugins/affiliates/" rel="ugc">Affiliates</a> or <a href="http://www.itthinx.com/shop/affiliates-pro/" rel="nofollow ugc">Affiliates Pro</a> or <a href="http://www.itthinx.com/shop/affiliates-enterprise/" rel="nofollow ugc">Affiliates Enterprise</a></li>
<li><a href="https://wordpress.org/plugins/captcha/" rel="ugc">Captcha</a></li>
</ul>

Affiliates Captcha

Affiliates, Affiliates Pro and Affiliates Enterprise integration with the Captcha plugin.

refersion

Refersion for WooCommerce

Works great!

Seamlessly connect your WooCommerce shop with Refersion and start tracking sales driven by promoters, influencers, and affiliates!

Affiliates Captcha vs Refersion for WooCommerce