Like so many other items in the company's lineup, the Arc has a soft-touch back, adorned with a diamond pattern of criss-crossed lines.

ENGADGET: Kobo Arc tablet hands-on (video) Hands-on

Some are simple in their approach, such as the MotionCAPTCHA project that requires tracing a pattern with the mouse pointer or Capy, a service in beta for touch-based devices.

FORBES: Artificial Intelligence Will Defeat CAPTCHA -- How Will We Prove We're Human Then?