Hardeep Asrani

This plugin adds Google’s reCAPTCHA form to your BuddyPress’ registration page to keep your community spam-free! You can use out simple option panel to add reCAPTCHA credentials right from your Dashboard without editing any files.
This plugin is a forked version of <a href="https://wordpress.org/plugins/buddypress-recaptcha/" rel="ugc">BuddyPress reCAPTCHA</a> plugin, which requires you to edit plugin core files to configure reCAPTCHA.

BuddyPress Captcha

This plugin adds Google's reCAPTCHA form to your BuddyPress' registration page to keep your community spam-free! You can use out simple opti …

edwardw

This plugin is just a very effective yet simple plugin which adds a question to the comment form that blocks most automated spam-bots by making them answer a common sense question. For optimal effectiveness, you should add multiple questions so that the spambots can’t “memorize” the question and answer. The plugin will display questions at random to prevent the aformentioned memorization. Multiple answers can be added per question to account for variances in answers. (e.g. “five”, “Five”, “5”)
Plugin homepage: http://www.compdigitec.com/apps/wpnobot
Please drop a <a href="http://www.compdigitec.com/labs/2011/10/09/wp-no-bot-question-plugin-for-wordpress/" title="WP No-bot Question plugin for WordPress" rel="nofollow ugc">comment</a> if it works for you, if you found any bugs or if you have suggestions/ideas for this plugin – complaints welcome!

WP No-Bot Question

Simple question that blocks most spambots (and paid robots) by making them answer a common sense question

BuddyPress Captcha vs WP No-Bot Question