CAPTCHA for WordPress that integrates into login, registration and comments.
https://wordpress.org/plugins/wp-math-captcha/
Widgets · CAPTCHA · WordPress Plugins
Get access to data on 33,620 websites that are Math Captcha Customers. We know of 27,236 live websites using Math Captcha and an additional 6,384 sites that used Math Captcha historically and 12,950 websites in the United States.
Get a list of 33,620 websites using Math Captcha which includes location information, hosting data, contact details, 27,236 currently live websites and an additional 13,114 domains that redirect to sites in this list. 6,384 sites that used this technology previously and 12,950 websites in the United States currently using Math Captcha.