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.
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reCAPTCHA - reCAPTCHA is a free security service that protects your websites from spam and abuse.
Enigmail - Security extension to Mozilla Thunderbird and SeaMonkey
GeeTest CAPTCHA - GeeTest protects your websites, mobile Apps and APIs from bot threats.
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