Kasuga

Tiny Comment Spam Blocker is a lightweight yet powerful plugin designed to protect your WordPress comments from spam. It employs five different techniques to detect and block unwanted comments:
<ol>
<li>Nonce Verification – Ensures that the comment form submission is genuine.</li>
<li>Submission Time Check – Blocks comments submitted too quickly to prevent bots.</li>
<li>Honeypot Field – Hidden field that traps automated spam bots.</li>
<li>User Agent Validation – Detects suspicious User-Agent strings and blocks them.</li>
<li>Forbidden Word Filtering – Blocks submissions containing words or phrases from a configurable list within the comment body, email address, or IP address.</li>
</ol>
These filters are applied in order: if a comment passes the first check, it proceeds to the second, and so on, until all checks are applied or the comment is blocked.
Additional features:
<ul>
<li>Option to log detected spam in a local log file (up to 1.0 MB).</li>
<li>Optional email notifications when spam is detected.</li>
<li>Easy settings page in the WordPress admin panel.</li>
</ul>
<h3>Settings</h3>
The plugin provides the following settings in the WordPress admin panel:
<ul>
<li>Enable Spam Protection – Toggle the spam protection on or off. When disabled, all anti-spam checks are skipped.</li>
<li>Save Spam Detection Log – Enable or disable logging of detected spam. Logs are saved in a local file up to 1.0 MB within the WordPress uploads directory.</li>
<li>Notification Email Address – Enter an email address to receive notifications when spam is detected. Leave blank to disable email notifications.</li>
<li>Minimum Submission Time (seconds) – Set the minimum allowed time between loading the comment form and submitting a comment. Comments submitted faster than this threshold are considered spam.</li>
<li>Forbidden Words List – Enter one forbidden word, phrase, or IP address per line. Submissions containing these entries in the comment body, email address, or IP address will be blocked. Case is insensitive.
<ul>
<li>Example: 
viagra 
online pharmacy 
spam@email.com 
164.138.205.72</li>
</ul>
</li>
</ul>
<h3>Arbitrary Section</h3>
This plugin is designed to be lightweight and fast, ensuring minimal impact on site performance while providing robust protection against comment spam.

Tiny Comment Spam Blocker

A simple and lightweight yet rock-solid plugin that blocks comment spam using multiple automatic detection methods.

Olaf Lederer

This free contact form plugin is used to create accessible contact forms with advanced spam protection (honeypot, cookie and optionally Cloudflare Turnstile or hCaptcha). In contrary to most other form plugins, there is no form-builder included.
<h4>Features</h4>
<ul>
<li>The generated form is accessible and works even when the visitor has disabled Javascript</li>
<li>Accessible form field validation</li>
<li>Protect your forms against spam bots using a honeypot and cookies</li>
<li>Track successfully submitted forms in Google Analytics and/or Clicky</li>
<li>Create multiple contact forms via an easy to use interface and add the form via the block editor or using a shortcode</li>
<li>Collect form submissions for all your forms or the forms you choose</li>
<li>Get insights which spam protection feature works the best for your form. A simple log file keeps track about the different spam attempts</li>
<li>Multiple responder emails, send a HTML formatted mail in response to the form submission</li>
<li>Works with the default wp_mail() function (use it together with the <a href="https://wordpress.org/plugins/simple-smtp-by-maileroo/" rel="ugc">Maileroo</a> plugin to send emails via SMTP)</li>
<li>Optional: Protect your forms by blocking specific countries which are not relevant for your website or business</li>
<li>Optional: Protect your contact form with the plugin <a href="https://wordpress.org/plugins/honeypot/" rel="ugc">WP Armour – Honeypot Anti Spam</a></li>
<li>Optional: Email address verification with the verification API from <a href="https://maileroo.com/?r=acfplugin" rel="nofollow ugc">Maileroo</a></li>
<li>Optional: Form fields for Company name, phone number, website and an accept terms checkbox</li>
<li>Optional: Redirect the visitor after a succesful form submission to a “Thank you” page</li>
<li>Optional: Use the plugin’s CSS style-sheet for your forms</li>
<li>Optional: Protect your forms with Cloudflare Turnstile or hCaptcha</li>
<li>Optional: For additional spam protection, you can add a simple and accessible challenge to your form.</li>
</ul>
The plugin is built to keep stuff simple. If you need a complex web form or if you need a form builder, please use one of the form plugins you can find in the WordPress repository. To use the “Block countries” feature we use the IP to Country API from Country.is. They offer a free service and you don’t need an API key.

Ajax Contact Form

An easy to use contact form plugin with multiple inbuilt features to prevent contact form spam.

Tiny Comment Spam Blocker vs Ajax Contact Form