CAPTCHaStar! A Novel CAPTCHA Based on Interactive Shape Discovery

Mauro Conti, Claudio Guarisco, Riccardo Spolaor

Abstract: Over the last years, most websites on which users can register (e.g., email providers and social networks) adopted CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) as a countermeasure against automated attacks. The battle of wits between designers and attackers of captchas led to current ones being annoying and hard to solve for users, while still being vulnerable to automated attacks.