CAPTCHA?

Have you ever wondered why we are prompt to "I'm not robot" checkbox or an image with several distorted letters?

What’s the propose of the Captcha?

Captcha stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”. In other words, CAPTCHA determines whether the user is real or a spam robot.

CAPTCHAs were invented to block spammy software from posting comments on pages or purchasing excess items at once.

Who uses Captcha?

Captcha is used by the website that want to verify that the user is human or not before moving further. CAPTCHA is used in registration forms on websites such as Yahoo! Mail or Gmail where people can create free accounts. CAPTCHAs prevent spammers from using bots to create a plethora of spam email accounts.

How does a CAPTCHA work?

Classic CAPTCHAs, which are still in use on some web properties today, involve asking users to identify letters. The letters are distorted so that bots are not likely to be able to identify them. To pass the test, users have to interpret the distorted text, type the correct letters into a form field, and submit the form. If the letters don't match, users are prompted to try again. Such tests are common in login forms, account signup forms, online polls, and e-commerce checkout pages.

The idea is that a computer program such as a bot will be unable to interpret the distorted letters, while a human being, who is used to seeing and interpreting letters in all kinds of contexts – different fonts, different handwriting's, etc will usually be able to identify them.

But as the technology has been evolving, machine learning can read the distorted letter. So, to tackle this problem, google came with a new concept reCAPTCHA.

Google reCAPTCHA has developed no. of another test to sort human and user, which is further advance then the classical CAPTCHA.

Google reCAPTCHA type of test include:

1.      Image recognition.

2.      Checkbox.

3.      General user behavior assessment.

1.Image recognition:

For an image recognition reCAPTCHA test, typically users are presented with 9 or 16 square images. The images may all be from the same large image, or they may each be different. User has to identify the object in image (that is ask in the question) and click the following box which is the answer. If their response matches the responses from most other users who have submitted the same test, the answer is considered "correct" and the user passes the test.

2.Checkbox:

Most interesting topic of all. This page i.e. I am not robot page which less user-friendly tracks your mouse movement until you reach the checkbox and according to the movement it decides whether the user is human or not. It tracks your movement because if a bot checks the box the movement of the bot, will be straight and precise or we can say predictable until it reaches the box.

Note: The reCAPTCHA also may assess the cookies stored by the browser on a user device and the device's history in order to tell if the user is likely to be a bot.

If the reCAPTCHA can not verify though this method it will prompt the user to another method.

3.General user behavior assessment:

The latest version of captcha where the user is not prompt with the challenge. Here the program check the user’s history of interaction on the internet and according to that it differentiate human and bot. Most the program can do the task of sorting the human and bot but if it not able to sort then the user is prompt with the other reCAPTCHA challenge.

When does the CAPTCHA gets triggered?

Majority of the times it when the CAPTCHA popup it’s the website properties to defend the site from bots. Other  time it get prompt if the users activity match like bot i.e. when the user click the hyperlink at far high rate than normal.