Date Added: Jun 2012
A CAPTCHA is a technique that is used to prevent automated programs from being able to acquire free e-mail or online service accounts. However, as many researchers have already reported, conventional CAPTCHAs could be overcome by state-of-the-art malwares since the capabilities of computers are approaching those of humans. Therefore, CAPTCHAs should be based on even more advanced human-cognitive-processing abilities. In addition, it is also important to keep in mind that answering CAPTCHAs is an added annoyance for users, who feel troublesome to prove that they are humans at every Web accesses.