jammycakes

This plugin rejects outright any comments that contain either (a) BBCode 
[url=…] tags or (b) more than a predefined number of hyperlinks. As comments 
of this nature are almost exclusively spam, this should cut down drastically on 
the amount of detritus that Akismet has to deal with, making it easier to check 
for false positives in your spam queue.
<h3>Configuration</h3>
The default settings enforce a limit of two hyperlinks per comment. 
To change this, edit the number in the line just below the copyright notice 
which says:
<pre><code>define('MAX_HYPERLINKS', 2);
</code></pre>
If you set it to zero, it will not allow any hyperlinks. To allow unlimited 
hyperlinks and only block BBCode, comment out this line.
<h3>Redistribution</h3>
Copyright (c) 2007 James McKay 
http://www.jamesmckay.net/
Permission is hereby granted, free of charge, to any person obtaining a copy 
of this software and associated documentation files (the “Software”), to deal 
in the Software without restriction, including without limitation the rights 
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
copies of the Software, and to permit persons to whom the Software is 
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in 
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.
<h3>Reporting bugs</h3>
When reporting bugs, please provide me with the following information:
<ol>
<li>Which version of Comment Timeout you are using;</li>
<li>Which version of WordPress you are using;</li>
<li>The URL of your blog;</li>
<li>Which platform (Windows/IIS/PHP or Linux/Apache/MySQL/PHP) your server 
is running, and which versions of Apache and PHP you are using, if you 
know them;</li>
<li>The steps that need to be taken to reproduce the bug;</li>
<li>If possible, any relevant information on other plugins or configuration 
options that you may think appropriate.</li>
</ol>
See the following blog entry for further guidance on troubleshooting and 
reporting problems:
http://www.jamesmckay.net/2007/04/how-to-report-issues-with-wordpress-plugins/
<h3>For more information</h3>
For more information, please visit the plugin’s home page:
http://www.jamesmckay.net/code/link-limits/
The Mercurial repository and issue tracker for this plugin are at:
http://bitbucket.org/jammycakes/link-limits/

Link Limits

Rejects comments that contain BBCode or too many hyperlinks.

webvitaly

kudlav

This is fork of successful Anti-spam plugin v5.5 written by webvitalii, for more info visit <a href="https://github.com/kudlav/anti-spam/" rel="nofollow ugc">GitHub Fork</a>. 
From version 5.6 maintained by kudlav.
<ul>
<li><a href="https://github.com/kudlav/anti-spam/" rel="nofollow ugc">GitHub</a></li>
</ul>
Anti-spam Reloaded plugin blocks 100% of automatic spam messages in comments section and also blocks all trackbacks.No captcha required.
Plugin is simple and easy to use: just install it and it just works.
Blocked comments can be stored in the Spam area and converted to regular comments if needed.
Anti-spam Reloaded plugin is GDPR compliant and does not store any other user data except of the behaviour mentioned above.
Plugin blocks spam only in comments section.. 
Plugin does not block manual spam (submitted by spammers manually via browser).
<h3>Compatibility</h3>
All modern browsers and IE11+ are supported. 
Anti-spam Reloaded plugin works with disabled JavaScript. Users with disabled JavaScript should manually fill current year before submitting the comment.
Server compatibility:
<ul>
<li>WordPress 3.3 – 6.5</li>
<li>PHP 5.6 – 8.2</li>
<li>Doesn’t use jQuery</li>
</ul>
Plugin is incompatible with:
<ul>
<li>Disqus</li>
<li>Jetpack Comments</li>
<li>AJAX Comment Form</li>
<li>bbPress</li>
</ul>
If site has caching plugin enabled and cache is not cleared or if theme does not use ‘comment_form’ action 
and there is no plugin inputs in comments form – plugin tries to add hidden fields automatically using JavaScript.
<h3>How does it work?</h3>
The blocking algorithm is based on 2 methods: ‘invisible js-captcha’ and ‘invisible input trap’ (aka honeypot technique).
<h4>‘invisible js-captcha’</h4>
The ‘invisible js-captcha’ method is based on fact that bots does not have JavaScript on their user-agents. 
Extra hidden field is added to comments form. 
It is the question about the current year. 
If the user visits site, than this field is answered automatically with JavaScript, is hidden by JavaScript and CSS and invisible for the user. 
If the spammer will fill year-field incorrectly – the comment will be blocked because it is spam.
<h4>‘invisible input trap’</h4>
The ‘invisible input trap’ method is based on fact that almost all the bots will fill inputs with name ’email’ or ‘url’. 
Extra hidden field is added to comments form. 
This field is hidden for the user and user will not fill it. 
But this field is visible for the spammer. 
If the spammer will fill this trap-field with anything – the comment will be blocked because it is spam.

Link Limits vs Anti-spam Reloaded