For the last 12 years or so “Captchas” have been the standard way of making sure it is a human rather than a virtual robot that is entering a web-based service. You will have seen them, typing into two rather hard-to-read words or a string of jumbled up characters. It can be hard, however, to hit the balance between being hard enough to keep out the “spambots” while being simple enough not to put off potential customers who want to sign-up for a service.
A Minteye Captcha appears as a scrambled image with a small slider below it. The user has to move the slider until the image looks correct, which may happen at any point. Minteye’s software determines if you’ve moved the slider to the correct position, at which point it lets the website know that you are a human so you can continue navigating…
The idea for Minteye came from founder Shayke Inbar, who has dyslexia and found it extremely difficult to pass standard Captcha tests. Seeking to create a similar test that used images rather than letters, he realized that using ads for those images could generate money while authenticating users.
MIT Technology Review: Sliding Images Fool Spambots Without Driving You Mad