Yes, we're talking about those annoying puzzles confirming you're not a robot, every now and then, when you're surfing the internet. But, how does a CAPTCHA work exactly?
Well, first of all, the word CAPTCHA is actually an acronym which stands for Completely Automated Public Turing test to tell Computers and Humans Apart. And it is designed to do exactly that!
The biggest issue many online services face is automated programs that do unwanted things on their sites. A prime example of that is when you hop online to make a purchase of a limited edition product. Say there are a limited number of tickets available for a concert, and the online purchasing is made live to the public at a set time. A bot can make multiple purchases in a fraction of a second, and then you, as a human, find out all the tickets have been sold already!
So, to prevent this, a CAPTCHA is set in place to filter out bots. CAPTCHA's are designed in multiple different ways, such as picture selection methods, audio methods and word ones too.
But what about Google's simplistic method, where all you have to do is click the box that says "I'm Not A Robot"? Surely a bot can click the button? Well, yes, it can. What this system does, though, is measure the way you move your mouse. Humans have a random mouse pattern where bots are usually linear, so therefore, CAPTCHA can identify who is who.
Take a look at the video below by YouTube channel, Tech Quickie, on How Does A CAPTCHA Work?