CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. For the non-computer scientists in the audience, that may beg the question, but the bottom line is that it is a mechanism to hopefully limit the amount of spam we get from our contact and other web forms.
For the most part, it works splendidly. When you realize that most of the email coming from your website is junk and not real people trying to contact you, you add something called CAPTCHA to the form. Real folks are a bit annoyed because they have to interpret some garbled letters and numbers, but the robots in cyberspace are confused and you have a little less junk to delete from your inbox. Life is better.
Of course, over the years the original CAPTCHA concept has evolved. Like many others, I moved from using plain CAPTCHA to the re-CAPTCHA service. Yes, it doubles the number of words you have to decipher, but the prize is that one of those two words is work that you are doing to make the world a better place. You are deciphering a word from some ancient, out-of-print book in order that the rest of us may be able to read it on our computer, iPad or Kindle. Life improves.
There are, sadly, two problems with all of this. Firstly, I don't know about you, but for me, it is rare that the CAPTCHA or reCAPTCHA I have to solve is as legible as the examples I've provided here (from Wikipedia.org and captcha.net). It's extremely frustrating when you're in a hurry to complete something and you can't negotiate this roadblock. Secondly, there's more than one kind of robot out there trying to break through your carefully constructed form. For simplicity, I'll say that there are two kinds of robots: smart ones and stupid ones.
Stupid robots are easily distracted by our schemes to preclude them. Smart ones aren't. Which leaves us in a sort of a quandry. Are we forced to put up with the smart robots or is there another way?
Where there is a will there is a way. For this reason, I don't believe that any system that we can devise won't be broken by someone who only sees it as a challenge. However, we can switch strategies to keep them at bay. The new strategy that I've discovered and implemented successfully is called PlayThru by the geniouses at areyouahuman.com. Rather than guessing words or numbers, we are invited to play a short game. Not only are the tiny games charming, so far, the robots plaguing me are on hiatus.