lelandf

Stop Signup Spam will prevent user registration of anyone trying to sign up with an the email address or IP address that has been reported to <a href="http://stopforumspam.com/" rel="nofollow ugc">Stop Forum Spam</a>.
Contrary to what the name implies, Stop Forum Spam can be used with any web service, not just forums.
At this time, Stop Signup Spam integrates with:
<ul>
<li>The core WordPress registration form</li>
<li>Restrict Content Pro</li>
<li>MemberPress</li>
<li>Give</li>
</ul>
By installing this plugin, you consent to an API call sent from your WordPress site to Stop Forum Spam after every attempted user registration. The API call includes the user’s email address and IP address.
It is a similar concept to <a href="https://wordpress.org/plugins/akismet/" rel="ugc">Akismet</a>, except instead of checking for blog comment spam, it checks for user signup spam.
Unlike Akismet, no API key is required to query Stop Forum Spam’s database. Partly because of this, I decided not to include a settings page in the Stop Signup Spam plugin. Just activate and you are all set.
The plugin does not log any user registration info. Any data sent to Stop Forum Spam would fall under their <a href="https://www.stopforumspam.com/privacy" rel="nofollow ugc">privacy policy</a>.
Please note that Stop Forum Spam is a third-party service that I have no affiliation with. I just found it, could not find any existing WordPress plugins that worked with it, and built one myself.
It has helped me cut down on signup spam on a free membership site that I run, and I hope it will help you do the same.

Stop Signup Spam

Check user registration info against the Stop Forum Spam database before allowing registration

Stop Signup Spam vs hCaptcha for WP