FriendlyCaptcha is a proof-of-work based CAPTCHA alternative that respects the user's privacy, see the Friendly Captcha website.
Install Friendly Captcha for WordPress.
Make sure you have PHP installed (e.g. with brew install php on a Mac).
cd friendly-captcha
mkdir -p bin
php -r "copy('https://getcomposer.org/installer', './bin/composer-setup.php');"
php bin/composer-setup.php --install-dir=bin --2.2bin/composer.phar installThe friendly-captcha directory is now ready to be installed as a Wordpress plugin by copying it into the wp-content/plugins directory of your site.

