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…

Kevin Pirnie

This is yet another plugin that attempts to block spam form posts. We attempt to do so using some online list resources and block based on what we find throughout. We then mark the post as spam, and prevent any email from being sent from the site.
As of right now, this only checks the comment forms. We are working to build the checks into the major form builders.
<h3>Features</h3>
Checks form content against a massive list of potential spam words, checks form poster email addresses against a massive list of known spam email domains, checks the form posters IP address against a massive list of known spam IP addresses, and then checks the online DNSBL’s for listings.

Kev's Spam Stop

Plugin to attempt to stop spam form submissions.

Anti-Spam Zapper for WordPress vs Kev's Spam Stop