captcha is a type of challenge-response test Used in computing as an attempt to Ensure That the response is not generated by a computer. The process usually involves one computer (a server) Asking a user to complete a simple test the which the computer is Able to generate and grade. Because other computers are supposedly Unable to solve the CAPTCHA, any user entering a correct solution is Presumed to be human.
sometimes when I have to write a post or log into a site that we are required to rewrite the captcha given to assure that we are not a machine, this is a good security system but sometimes it makes our captcha hassle and some time ago I happened to get a captcha is troublesome, damn ... I have to ask for another re-captcha to be posting in a forum.
This is a troublesome captcha image:
