What are the best practices to implement a secure CAPTCHA?

Also I want to know:
What is the best way to identify an insecure CAPTCHA?

  • These are 2 very, very different questions. As for your first, have you seen the documents online that specify how to do this? – schroeder Nov 3 '15 at 23:39
  • no, can you share me good documentation please? – hmrojas.p Nov 4 '15 at 0:04
  • We require that you have done a little research before posting here. Please look up how other implementations work and then come back with specific questions about what you still need help with, – schroeder Nov 4 '15 at 0:42
  • Ok I understand, sorry – hmrojas.p Nov 4 '15 at 14:51