Web-security under serious trouble, a group of hackers from Defcon Group 949 managed to crack Google's reCAPTCHA system with a success rate of better than 99 percent. Last week in LayerOnesecurity conference in Los Angeles they demonstrated their research. But just an hour before the presentation, Google made improvements to its CAPTCHA system and fixed those flaws.

In their site they said - that they have developed everything using Ubuntu 10.04, Ubuntu 11.04, and Debian 6, however it should work on any Linux distribution without too much effort. The one thing we noticed when testing it on Ubuntu 12.04 is that it comes with a slightly different version of SoX, which has some changes which drops accuracy from 99% to around 60%. So for best results, you'll want to use SoX v14.3.0 (or v14.3.1). 

They have also developed a tool named "Stiltwalker" a proof of concept tool that defeats Google's reCAPTCHA with an insanely high accuracy (99%). All the research, code, tools and examples used in the reCAPTCHA domination made available to download for all.