webvitaly

<ul>
<li><a href="http://web-profile.net/wordpress/plugins/fortify/" title="Plugin page" rel="nofollow ugc">Fortify</a></li>
<li><a href="http://web-profile.net/donate/" title="Support the development" rel="nofollow ugc">Donate</a></li>
<li><a href="https://github.com/webvitalii/fortify" title="Fork" rel="nofollow ugc">GitHub</a></li>
</ul>
Fortify plugin blocks automatic spam in comments section. No captcha.
Plugin is easy to use: just install it and it just works.
Blocked comments can be stored in the Spam area if needed. This can be enabled/disabled via Settings page. This is useful for testing and debug purpose. Blocked spam comments can be easily converted to regular comments if needed.
Fortify plugin is GDPR compliant and does not store any other user data except of the behavior mentioned above.
Plugin blocks spam only in comments section.
After installing the Fortify plugin try to submit a comment on your site being logged out. 
If you get an error – you may check the solution in the <a href="https://wordpress.org/support/plugin/fortify" rel="ugc">Support section</a> or submit a new topic with detailed description of your problem.

Fortify

Ostap Mykhaylyak

Light and invisible method to block spam when spam is posted.

SpamScout

Light and invisible method to block spam when spam is posted.

Fortify vs SpamScout