Familiar with these? Yeah, these are the images that appear on gmail when you enter your email id/password incorrect for more than 3 times. You see similar “images” while downloading stuff from rapidshare and posting links on orkut. These are called CAPTCHA images. Captcha stands for Completely Automated Public Turing test to tell Computers and Humans Apart. As the name goes, it aims at developing tests (in the form of images) so as to prevent bots from downloading files or making accounts. These images are developed by various algorithms which mainly distort the text that is input, and the output is an image. It is near impossible for any program to decode the captcha on its own. Though I guess that it can be broke if one has the algorithm by the image was distorted. Many attempts are made to decode these without human intereference, i mean without the need for humans to enter it. And some do succeed, but the success rate is quite low. Recently, it was reported that google’s captcha codes were cracked, but as i said, the success rates were too low. The guy analysed google’s data, traffic and many other things, found out the servers that were used for generating captchas (yeah, they use 2 different server connections to make a captcha), but yet, he got a low success rate.
And yes, programs are available on internet which allows making multiple accounts at the same time, without filling the details like name etc. These ids are then used to spam you. Even though captcha has been implimented, there hasn’t been much difference in spamming and all. And for automated account making, the programs now simply display the captcha image that it cannot recognize. So, ultimately you have to just sit down and write the text in the captcha image. A little slower than before, but yet fast to make enough fake-ids.
Here is a link for gimpy. Its an article on breaking a visual CAPTCHA. Hmm…did you notice? This time i wrote “visual” CAPTCHA. The one other that I know is audio captcha, i.e. you have to listen to an audio file and then enter the text you hear. I saw this one while registering for an paypal account. Check it out if you like.
Thats all folks. If there’s any correction/query, kindly comment.
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