DesignSmoke

Anti-Spam Zapper will automatically remove spam comments and block spambots without annoying CAPTCHAs.
Protect your website from spam comments and automated spam using this free WordPress anti-spam plugin.
Features
<ul>
<li>Protect Comments</li>
<li>Block Spambots</li>
<li>Marks comments as spam, without deleting them, just-in-case there’s a false positive</li>
<li>Nothing to fill out, completely silent action</li>
</ul>
FAQ
<ul>
<li>Does this require javascript?</li>
<li>
Yes, however the vast majority of users have javascript enabled (over 99%). Users with javascript disabled will be shown a message, just to make sure nothing is lost.
</li>
<li>
Can I modify this plugin?
</li>
<li>Yes! The plugin is <a href="http://www.gnu.org/licenses/gpl-2.0.html" rel="nofollow ugc">licensed under the GPLv2 License</a>.</li>
</ul>
Upgrade to Pro
Want to protect your contact forms too? <a href="https://www.designsmoke.com/anti-spam-zapper-wordpress-plugin/" rel="nofollow ugc">Upgrade to Anti-Spam Zapper PRO by DesignSmoke</a> to stop all spam comments and form submissions on your WordPress website or WooCommerce store.

Anti-Spam Zapper for WordPress

Anti-Spam Zapper will automatically remove spam comments and block spambots without annoying CAPTCHAs. Protect your…

willjenkins

Using the most effective features of other spam programs. Astounding Spam Prevention effectively guards against comment spam and registration spam without the use of a Captcha. 
This is a fork of the original Stop Spammers Spam Prevention and uses some of the code, but it is greatly simplified so it is not as aggressive and will not prevent a user from logging in. It does not interfere with jetpack and does not know about WooCommerce so there are no conflicts. Unlike Stop Spammers it does not check logins, but only checks registrations and comments. 
It also repairs many bugs that I found in the Stop Spammers plugin and has many new methods for detecting spam.
<h3>Donate</h3>
Please buy one of my books and give it a good review. I worked hard on these books, and they are worth reading. 
See my books and contacts: https://linktr.ee/keithpgraham

Astounding Spam Prevention

Based on Stop Spammers, this lightweight spam stopper is still aggressive enough to stop 99% of the spammers and robots hitting your site. It is careful to never lock a webmaster out of WordPress. The options interface is slick and the logging is very very useful. 
I use it on 11 of my sites and I have my clients all using it.
Thanks to Will and all the effort he put in to make this plugin extremely useful while still being very very safe.

Works like a charm

It kills the spam

Got dozens of registrations after installing and activating all options. It made no difference what options were set. Uninstalled.

Made no difference to the spam

Very effective anti-spam plugin that eliminates comment spam, and registration spam. Combines many effective methods for identifying spammers and keep …

Anti-Spam Zapper for WordPress vs Astounding Spam Prevention