unCAPTCHA

CAPTCHAs are the Internet's first line of defense against automated account creation and service abuse. Google's reCaptcha, one of the most popular captcha systems, is currently used by hundreds of thousands of websites to protect against automated attackers by testing whether a user is truly human.

We present unCaptcha, an automated system that can solve reCaptcha's most difficult auditory challenges with high success rate. We have evaluated unCaptcha using over 450 reCaptcha challenges from live websites, and showed that it can solve them with 85.15% accuracy in 5.42 seconds, on average: less time than it takes to even play the audio challenge!

unCaptcha combines free, public, online speech-to-text engines with a novel phonetic mapping technique, demonstrating that it requires minimal resources to mount a large-scale successful attack on the reCaptcha system.

To put it simply: talk is cheap!