Importance of Captcha and How it works?


If you are frequent surfer of the web world,then you must be familiar with the word CAPTCHA. If not, they are those twisted words which enable or block entries into websites.Commonly, you must have seen Captcha while trying to post an ad, or trying to comment on a blog post, or filling up a form. In simple words, CAPTCHA stands as a gatekeeper controlling your entry and judging whether you are a human or a bot (spamming machine).

CAPTCHA is a abbreviation of “Completely Automated Public Turing test to tell Computers and Humans Apart”. CAPTCHA is basically a program that distinguishes between human and computer. These are mainly colorful images with distorted text, used at last section of Web registration forms in many websites. CAPTCHA are used by many websites to avoid spamming from “bots,” or automated programs or Scripts generally written for “spam” or “abuse”. These distorted images can be easily read by humans and not by computer generated programs, and thus bots can never browse sites protected by CAPTCHA. Some kinds of bots attack are harmful for a web site.

Security and accessibility are the two main key points that a CAPTCHA satisfies. The first point of security is completely satisfied by providing a great protection from bots and spams. The latter point is a bit on the verge of big challenge, as a CAPTCHA is based on the picture vision or text distortion which are hard for the dyslexic users and impossible for physically disabled users.

But we all know, that CAPTCHAs are playing an important role in keeping the website spam-free and safe from bot-attack, hence making everyone’s experience quite better.


How to Create CAPTCHA?

CAPTCHAs are mainly created by using programming languages like PHP or ASP. The code should consist of three main functions. First, the code should generate a random text or image consisting of distorted alphabets or digits or combination of both. Then in second step,it should validate or check the provides user answer. And finally, at third step it should make these pictures secure. To make the code more challenging you can “Rotate the text at random angles, add uneven spaces in between characters, use a TTF(True Type Fonts) fonts and change the font randomly every time, use a random text and image size every time, use more advanced text distortion and colors, move the lines across or over text randomly, and store the password in a random cookie”.

How CAPTCHA works?

CAPTCHA works as fooling the bots by asking questions that only human can answer. CAPTCHA fools or confuse bots by generating such pictures or text containing distorted letters -different pictures with different letters in different shapes are generated randomly- Then CAPTCHA asks the user to enter the letters shown in the picture mainly at the last of the form . Bots unable to recognize the distorted letters fails the Captcha test. After the user submits the answer CAPTCHA validate the answer.

Importance of CAPTCHA

1. Shielding Registration Forms in Websites from bots

Large number of websites such as Gmail, Facebook, Twitter,Hotmail, Yahoo, and many more provide free user registration. Therefore, to authenticate the registration process, these websites have commonly used CAPTCHAs as a shield. In fact, for any site that is offering free registration, it is best to set up a CAPTCHA, so that all the registrations are done by humans and not programs or bots.

2. Filtering Spam Comments

By using CAPTCHA one can protect their website or blogs from spam comments, as on an average, bloggers receive more than 100 spam comments each day.

Spammers are capable of flooding a single post with hundreds of spam comments. And when such a thing happens, search engines such as Google, Yahoo or Bing would certainly assume that websites that are having lots of comments for a single post are inviting spams. So, to avoid this it is important for the website owners to make correct use of CAPTCHA, so that only human beings are capable of posting comments.

3. Avoiding Dictionary Attacks

CAPTCHAs also protects websites from dictionary attacks. Dictionary Attacks are the attacks in which an automatically generated scripts or computer program tries random passwords on login forms in case of an unsuccessful login. This is a method of breaking into a password-protected area of computer or server by continuously  entering each word of a dictionary serially  as a password.

4. Security During Online Shopping

Owners of online shopping sites also use CAPTCHAs within their site so that buyers can fill them before any kind of transaction procedure starts. In an online shopping method, the purpose of CAPTCHA is to validate that whether the person ordering products or services are humans only and thus bringing down the chance of receiving fake or spam orders.

5. Validating Email Account’s Owner

Email service providers such as Gmail and Yahoo, allows users to fill a CAPTCHA whenever they require to send large number of emails at a fast pace. As, there is high probability of your email account has been hacked by a malicious user or certainly a  hacker. Thus, securing your account from being misused.