The only technical details I could find on the site were: > The method is called biochronometrics and it maps behavior based on a series of complex algorithms.

The only technical details I could find on the site were: > The method is called biochronometrics and it maps behavior based on a series of complex algorithms. 5 million live tests show that bots can’t mimic human behavior when biochronometrics are applied. and: > NoMoreCaptchas analyses behavior while a user name and password are being entered and determines if the user is human or a bot. So presumably it monitors mouse and keyboard events during login; particularly the timing, judging from the name "biochronometrics"...