higherfield

Kaigai Spam Mail Blocker is a WordPress plugin that automatically detects and blocks spam or abusive contact form submissions, especially those originating from overseas.
The plugin analyzes submitted content and blocks messages that do not contain Japanese characters or consist primarily of alphanumeric characters, which are common patterns in spam messages.
Supported form plugins:
<ul>
<li>Contact Form 7</li>
<li>Elementor Pro Forms</li>
</ul>
No configuration is required. Simply install and activate the plugin.

Kaigai Spam Mail Blocker

Blocks spam submissions from overseas contact forms. Supports Contact Form 7 and Elementor Pro Forms.

filiw

Anti-Captcha is a transparent spam solution that does not require any end-user interaction. 
It is based on a nonce key, which is dynamically inserted using randomly generated (and obfuscated) javascript.
The aim of this plugin is to prevent automated attacks (by bots) on the following WordPress actions:
<ul>
<li>Posting comments</li>
<li>Registering for a new account</li>
<li>Requesting a lost password</li>
</ul>
When a comment is posted without a valid Anti-Captcha token, it shall be instantly marked as spam. This way, you can always manually approve this comment in hindsight if it appeared to be sincere.

Anti-Captcha (anti-spam botblocker)

Anti-Captcha is a transparent spam solution that does not require any end-user interaction.

Kaigai Spam Mail Blocker vs Anti-Captcha (anti-spam botblocker)