CAPTCHA type code was developed in the year 2000, it was created to prevent automated spam robots from filling out forms, sending out spam and carrying out other malicious activities on the internet.

CAPTCHA means ‘Completely Automated Public Turing Test to Tell Computers and Humans Apart’. It is a security feature used by a Website/blog to tell if it is communicating with a human or an automated spam robot.

CAPTCHA’s are useful in situations where it is absolutely essential to tell humans and machines apart, such as newsletter subscription, blog commenting, online registration, placing orders, filling surveys and e-commerce transactions.

Automated bots was primarily designed for sending spam for commercial promotional purposes, but more than ever, it is now being used for malicious purposes like harassment or vandalism.

Blog, forums and any comment-enabled site also use CAPTCHAs. With it they can be sure that no robot is commenting with the sole purpose of posting links to their website.

Though a human could filter the comments when it is a less busy or small websites. But as soon as growth begins, taking care of spam without any help can become a full-time job for many people. Therefore, the use of CAPTCHA is necessary.

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When selecting a CAPTCHA, 2 characteristics must be considered:

1. The CAPTCHA must be hard enough for a computer to understand.

2. The CAPTCHA must be easy enough for humans to understand.

Currently, most CAPTCHAs are distorted texts or characters mixed with other colors that are in the form of an image. Most of them also include the function to be heard on an audio file. It’s very useful if you have to enter a text that you can’t manage to read.

The most common complaint about the distorted word test is that some images were so complex, that even humans could not decipher them. People got tired of having to re-enter different CAPTCHA codes, a number of times, before a website accepted their form submission.

Also, blind users, who use screen readers and other tools to browse the Internet, were unable to see the words in the image for the CAPTCHA test.

Today, automated spam robots are getting smarter with the development of new technology. The creation of new algorithms, together with OCR, has enabled them to recognize the pattern of characters in images, even on noisy backgrounds. These issues have lead to the development of new systems of CAPTCHA.
Below are some of the CAPTCHA type:

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1. Captcha type – Angled Line captcha type: An angled line, struck through curvy text.

2. Captcha type – Pictures captcha type: Users are presented with a series of pictures, and asked to enter the common element among them or click on a specific picture.

3. Simple Questions captcha type: Users are asked simple math or word questions like ‘What is 47 + 11?’

4. Captcha type – Sound captcha type: An accessibility feature that is useful for blind users, this CAPTCHA plays an audio clip that reads out characters, which users have to enter in a text box.

5. Confirmation Page captcha type: A simple thank you page asks users to verify the information they have submitted.

6. Check Box captcha type: Users are asked to check a small box to confirm if they are humans

The BIG question now is: Which is the Most Secured CAPTCHA type?