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?

closed as too broad by schroeder Nov 4 '15 at 0:42

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 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