| Our days computers and Internet have evolved to the | | | | A common type of CAPTCHA requires that the user |
| point when software tools (such as standalone | | | | type the letters of a distorted image, sometimes with |
| programs or web scripts) can perform automated | | | | the addition of an obscured sequence of letters or |
| task on the web, such as navigating from website to | | | | digits that appears on the screen. This usualy ensures |
| website (spiders) filling and submitting web forms. | | | | that only humans can enter the correct answer, |
| This task was difficult many years ago, and people did | | | | because is difficult (but not impossible!) for machines to |
| not thought much about it back then. But now, with the | | | | extract the letters and digits from the image. |
| increasing amount of SPAM and the advanced script | | | | CAPTCHAs are common used expecially on web |
| languages, many hackers and spammers are writing | | | | forms, where the user is about to enter some sort of |
| and using scripts to automatically fill and submit forms. | | | | information, such as an URL, a comment, a post, or to |
| Many sites (all the major ones) are using a way to | | | | signup for some service, this will prevent automated |
| block automated submissions that is constantly | | | | software from performing actions such as: posting to |
| growing in popularity: CAPTCHA. | | | | blogs or forums, doing a large number of junk |
| A CAPTCHA (an initialism for "Completely Automated | | | | automated submissions, signups. |
| Public Turing test to tell Computers and Humans | | | | CAPTCHAs are by definition fully automated, requiring |
| Apart", trademarked by Carnegie Mellon University) is | | | | little human maintenance or intervention in administering |
| a type of challenge-response test used in computing | | | | the test. This has obvious benefits in cost and reliability. |
| to determine whether or not the user is human. | | | | |
