CAPTCHA
Image © reCaptcha
Image © reCaptcha



Description: Captcha is a program that secures websites from bots by generating random text that humans can read and repeat, but bots cannot. The way that they are able to keep bots from repeating the text is by distorting the words only slightly. Enough to deceive artificial intelligence but not enough to fool a human. It is used on many websites in order to stop automated software that would degrade the quality of the website through malicious actions, such as spam.

Throughout its lifetime, Captcha has seen several different versions. Early versions of Captcha were eventually able to be deciphered by certain programs available for sale such as PWNTCHA, AICAPTCHA, and BREAKING. These programs use Optical Character Recognition(OCR) along with simple algorithms in order to crack Captchas. There are also some spammers that pay about $0.80 to $1.20 for each 1,000 solved captchas to companies who employ human solvers in places like Bangladesh, China and India. Because of reasons like these, Captcha has to go through different versions frequently.

Below are two pictures of different versions of Captcha. The first one shows an early version that would soon be figured out how to be read by programs. The second picture is a modern version that uses angled lines that go through the word rather than warping the word itself.
captcha.jpg




captcha1.jpg


Newer versions of Captcha remain in the works. Since Captcha is currently limited to only a visual test, some users (such as those with disabilities) cannot pass the tests. For such cases, the use of an audio version of the Captcha could be implemented along with the visual version. However, this method is far from universally adopted and most websites remain using only the visual test.

sq-pix.png
One version of CAPTCHA called Squiggle-Pix, which instead of typing words, the user is required to trace their cursor around an object (in this case, a bobsled).

Applications:
  • Stop Comment Box Spam- Computers cannot recognize what is in the captcha. By using captcha, spam bots are prevented from flooding the comment box with spam ads for .

  • Secure Online Polls- Bots are able to vote as many times as programmed in online polls if they are not stopped. These can skew results and invalidate the poll. By using Captcha, all voters are recognized humans and the results will me more accurate.

  • Advertisments- Recently, Captchas have begun to use advertisements instead of random phrases, so that instead of a random Pair of words, the user sees a company slogan. While obnoxious, this has great marketing potential. The security of the system is dubious though, because a computer could be programmed to recognize the companies and their slogans.

  • Stopping Dictionary attacks- When a bot attempts to get into someone's online account by guessing the password, oftentimes both the user and the attacker will be locked out of the account. By using Captcha, a bot would not be able to guess at the passwords infinitely until lockout.

  • Teaching AI- 200 million captchas are solved each day. By using these human proofreaders, reCaptcha is able to correct words that it's own OCRs cannot identify.


Essentially anywhere you need to confirm that someone is human online, Captcha is a viable solution. Captcha technology prevents malicious computers from spreading spam and infiltrating webmail, as well as providing a way to improve computer technology.

Terminology:

  • OCR- Optical Character Recognizers, programs which regonize visual images and digitize that information. They are commonly used in the transcribing of books which which have not been transitioned into a digital format.

  • CAPTCHA- acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart"

Citations/References:

http://gizmodo.com/5643848/captcha-advertisements-annoying-squared
http://www.captcha.net/
http://en.wikipedia.org/wiki/Captcha
http://www.google.com/recaptcha/static/reCAPTCHA_Science.pdf
http://www.w3.org/TR/turingtest/