WordPress: Spam Protection by CleanTalk..
Max power, all-in-one, captcha less, premium anti-spam plugin. No comment spam, no registration spam, no contact spam, protects any WordPress forms. Formerly Anti-Spam by CleanTalk.
wordpress.org/plugins/cleantalk-spam-protect
This plugin is a free trial only, for ONE WEEK.
My use of this ended with the message:
Spam Protection by CleanTalk trial period ends, please upgrade to premium version!
My results were:
CleanTalk has blocked 22 spam.
CleanTalk Installed: Jul 4 2016
CleanTalk Trial ended: Jul 11 2016
Annual Fee:
Antispam package for 1 website, $9.99
Spam Protection by CleanTalk
https://wordpress.org/plugins/cleantalk-spam-protect/
Compatible up to: 4.5.3
Active Installs: 40,000+
Release Date: Unsure. But version 2.4.10 was on 2013-07-24 with version 5.44.1 on 2016-07-13
41 ONE Star Reviews
1340 FIVE Star Reviews
Alternative Anti Spam Plugins
All these are Compatible with latest WordPress 4.5.3, and show over 100,000 active installs.
Anti-spam
https://wordpress.org/plugins/anti-spam/
Compatible up to: 4.7
Active Installs: 100,000+
Release Date: 2012-09-06
3 ONE Star Reviews
110 FIVE Star Reviews
WP-SpamShield Anti-Spam
https://wordpress.org/plugins/wp-spamshield/
Compatible up to: 4.5.3
Active Installs: 100,000+
Release Date: 2014-10-03 (Forked from predecessor WP-SpamFree version 2.1.1.0, 2013-10-10)
12 ONE Star Reviews
516 FIVE Star Reviews
SI CAPTCHA Anti-Spam
https://wordpress.org/plugins/si-captcha-for-wordpress/
Compatible up to: 4.5.3
Active Installs: 300,000+
Release Date: 2008-08-21
15 ONE Star Reviews
72 FIVE Star Reviews
267.1 - 873,717