hCaptcha - Do you use a captcha to keep out bots? hCaptcha is a drop-in replacement for reCAPTCHA that earns website owners money and helps companies get their data labeled.
mosparo - the modern spam protection
GeeTest CAPTCHA - GeeTest protects your websites, mobile Apps and APIs from bot threats.
Mollom - Mollom is a freemium web service to get rid of spam, unwanted content and fake users on your...
MTcaptcha - Enterprise Captcha solutions
UniqPin - UniqPin is a free for non-commercial use service which destiny improve ability of interfaces detect...