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 38,595 websites that are Math Captcha Customers. We know of 28,727 live websites using Math Captcha and an additional 9,868 sites that used Math Captcha historically and 13,697 websites in the United States.
Get a list of 38,595 websites using Math Captcha which includes location information, hosting data, contact details, 28,727 currently live websites and an additional 13,372 domains that redirect to sites in this list. 9,868 sites that used this technology previously and 13,697 websites in the United States currently using Math Captcha.