CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) puzzles are designed to tell humans and bots apart on the web for reasons such as minimizing spam.

Different CAPTCHA services go about differentiating humans and bots in different ways, for example, distorting and skewing a series of letters to make them too difficult for automated programmes to decipher, but not so difficult that humans can't make them out.

Researchers have found that Google's Street View technology can decipher them with 99 percent accuracy, 'Gizmag' reported.

A company that Google bought in 2009, reCAPTCHA, takes a different approach that not only provides the security of a CAPTCHA form, but actually serves another purpose. reCAPTCHA is used to digitise old printed materials such as books.

It presents the user with two words that could not initially be read by computers - one that has previously been verified by a number of users and one that has not. In this way, it can both determine if a user is human and partially verify a new word.

Given the purpose and prevalence of CAPTCHAs, it's understandable that individuals with malicious intent may want to crack them.

Google does its own research into this so that it can improve the security of the reCAPTCHA service. As part of its research, it has applied the technology it uses for identifying house numbers in Street View to identifying CAPTCHA words.

The research found that the technology could "decipher the hardest distorted text puzzles from reCAPTCHA with over 99 percent accuracy."

As a result, Google suggests that answering a distorted image puzzle should not be the only factor used to distinguish a human from a machine.

Agencies