The cybercrooks attempting to defeat CAPTCHAs are no longer just traditional junk-mailers who want to get around the test to send spam. In a recent study, security researchers have discovered that criminals are also using circumvention techniques in attacks that harvest financial or personal data.
A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is commonly used to distinguish human users from computer automated applications, thus helping to prevent automated tools from abusing online services, such as webmail accounts. Hackers have developed numerous methods to bypass CAPTCHAs, including computer-assisted tools and crowd-sourcing, creating a cat-and-mouse game between miscreants and CAPTCHA providers such as Google and others.
Junk mailers, for example, are interested in defeating CAPTCHA challenges in order to establish webmail accounts for subsequent spam runs. Last weekend spammers managed to spam the UK's open data website by circumventing its CAPTCHA gateway in a slightly more sophisticated variant of the same play.
How do they do it?
Hackers are using computer-assisted tools based on optical character recognition or machine learning technologies as well as tools which outsource CAPTCHA-breaking to modern day sweatshops, typically located in India. More recently miscreants have begun hoodwinking naive users into being a part of the crowd sourced for CAPTCHA solutions. These crowd-sourcing techniques sometimes pose as CAPTCHA-busting games that reward players. Some CAPTCHA-busting sites offer free porn as an incentive.
News 10 months ago