Kofi Mokome

Enhance your website’s security and user experience with humanID – the anti-bot authentication created by the Foundation for a Human Internet, a nonprofit backed by Harvard and Mozilla. With humanID, your users can enjoy anonymity and seamless access, while automated and previously blocked users are stopped in their tracks. Say goodbye to frustrating CAPTCHAs and free up to 90% of your time spent reviewing comments, all while keeping your website secure. Whether you use WordPress or not, you can easily integrate humanID with your website’s contact form, including popular plugins like Contact Form 7. 
Try humanID today and see the difference it can make for your website’s security, user experience, and your own workload
<h3>How to Contribute</h3>
The source codes can be downloaded here <a href="https://github.com/human-internet/humanid-spam-filter" rel="nofollow ugc">GitHub</a>

humanID – Anti-Spam Comment Filter || Stop junk comments & Protect your users' privacy. 100% open source.

Replace ReCAPTCHA with a faster, user-friendly solution and block spammers & bots permanently

Umbrovskis.com

List of spammers in <a href="https://wordpress.org/plugins/wp-referrer-spam-blacklist/faq/" rel="ugc">FAQ</a>.
No need for configuration! Plugin in background redirects referral spammer to blank page ( about:blank ). Redirect link can be altered via filter <code>wp_referralblock_redirect_uri</code>.
NO auto update, as we see that as possible as security hole. We do not wan’t Your site to get hacked.
Plugin is for sites that can’t edit their <code>.htaccess</code> or configure NGINX or Apache servers.
Via <a href="http://go.mediabox.lv/1LbSuKq" rel="nofollow ugc">my LinkedIN post</a>: Few months ago I started to collect referral spam pages in private file un bitbucket.org. Problem was that I did not know all spammers. Then, few weeks ago, I found that Matomo (Open source analytics) started their own “project”, and they did the same thing I did – collected referral spam sites to block them from Your website.
On my own server I do that at server level, but some of my clients have hosting, where You can not edit server settings. This week I came up with another solution – WordPress plugin “WP referrer spam blacklist”. I will update list every week from <a href="https://github.com/matomo-org/referrer-spam-blacklist" rel="nofollow ugc">Matomo’s community-contributed list of spammers</a>.
If You have WordPress site and no knowledge about or access to server settings, I made that for You!
From <a href="https://en.wikipedia.org/wiki/Referer_spam" rel="nofollow ugc">Wikipedia</a>:
<pre><code>Referrer spam (also known as log spam or referrer 
bombing) is a kind of spamdexing (spamming aimed 
at search engines). The technique involves making 
repeated web site requests using a fake referer URL 
to the site the spammer wishes to advertise. Sites that 
publish their access logs, including referer statistics, 
will then inadvertently link back to the spammer's site. 
These links will be indexed by search engines 
as they crawl the access logs. 

This benefits the spammer because the free link improves 
the spammer site's search engine ranking owing 
to link-counting algorithms that search engines use.
</code></pre>
Other plugins by author: <a href="https://wordpress.org/plugins/itempropwp/" rel="ugc">itemprop WP for SERP/SEO Rich snippets</a> – Add schema.org itemprop code to the (custom) post content for search engines and bots for better SERP results

WP referrer spam blacklist (fight 2040+ Referrer Spammers in (Google/Matomo) Analytics)

WordPress plugin to fight with 2040+ referrer spammers (like semalt, buttons-for-website and many more).

humanID – Anti-Spam Comment Filter || Stop junk comments & Protect your users' privacy. 100% open source. vs WP referrer spam blacklist (fight 2040+ Referrer Spammers in (Google/Matomo) Analytics)