Paper about a novel generic approach to solving captchas using a single step that uses machine learning to attack the segmentation and the recognition problems simultaneously. Our tests show that this approac is able solve all the real world captcha schemes evaluated including Yahoo (5.33%) and ReCaptcha (33.34%), without any adjustments to the algorithm or its parameters. Our success against the Baidu (38.68%) and CNN (51.09%) schemes that use occluding lines as well as character collapsing leads us to believe that our approach is able to defeat occluding lines in an equally general manner.
This is the story of how — and why — Google switched to numeric captchas. Captchas are these wiggly words used as a puzzle to tell humans apart from computers. Over the last few years, based on my work that began at Stanford, I’ve been working on designing a more user-friendly captcha for Google that […]
This paper we describe how we designed a new CAPTCHA schemes for Google that focus on maximizing usability. Our new scheme which is now an integral part of Google sign-up and is served to millions of users, achieved a 95.3% human accuracy, a 6.7% improvement compared to the old one.
NuCaptcha is the first widely deployed video captcha scheme. Since Technology Review interviewed me about NuCaptcha in October 2010, I have been working on evaluating its security and usability. In this blog post, I will discuss how we are able to break the current version of NuCaptcha with >90% success and also discuss a possible […]
We show how using a generic approach, based on advanced audio processing and machine learning algorithm, our captcha breaker "Decaptcha" is able to break all the popular audio CAPTCHA schemes, including Microsoft and Yahoo.
Since I started doing research on CAPTCHA security two years ago, I have relentlessly collected samples of all the different schemes I have encountered. In this blog post, I want to share with you five of the most crazy, funny, and interesting schemes I collected.
We perform a mass-scale user study on how people react to the 21 most popular captcha schemes (13 images, 8 audios). This study reveals that even the most popular captchas scheme are often difficult for humans, with audio captchas being particularly problematic.