CAPTCHA stands for Completely Automated Public Turing test to tell
Computers and Humans Apart. A CAPTCHA is a type of challenge-response test used in computing to
determine whether or not the user is human.
You must have had a laugh when a website asked you to click on
not a robot thinking that can’t a robot click it.
The captcha is not used to stop humanoid robots from accessing a
website but to stop “bots”. These bots are just programmes/scripts thatare written to automatically visit the website. Why this automatic surfing is
harmful? Since these are computers visiting the website they can do it
very fast 1000s of times/second.
Let’s say you made a form to conduct a servey of how many students
wants a exam to be cancelled. If there is no captcha one can write a code
that can fill that form 1000s of time and therefore making the servey
One can write a script to request a data from a website over and over very
fast and that will result in delay in the response to legitimate clients or
may be result in the server to crash.