What is captcha?
Many sites use CAPTCHA security. You can see CAPTCHA when you
1. register on any site
2. are booking train or flight ticket
3. change password
4. put some link in scrap on orkut etc.
How does it look..
CAPTCHA is nothing but an image drawn in a style so only human can understand it. No software like handwriting recognition or pattern matching software, must be able to recognize them. As per their complexity you can find many types of CAPTCHA. Sometimes CAPTCHA is not an image. It might be a mathematics calculation. And you are supposed to enter its result.
CAPTCHA ensures human presence.
No but some good programmers can build application called virus which can download multiple files from a site or a single file multiple times. It may be used to increase number of hits to that file or with any other purpose. These scripts can be used to make a server down or with many other harmful purposes. So CAPTCHA is needful.
CAPTCHA saves you from brute force or dictionary attacks as well.
Hey! this is Amit Gupta (amty). By profession, I am a Software Eng. And teaching is my passion. Sometimes I am a teacher, as you can see many technical tutorials on my site, sometimes I am a poet, And sometime just a friend of friends...