Captcha Breaking :: Getting Naughty Once AgainPosted: February 12, 2009
Breaking CAPTCHA: Getting Naughty with Computer Vision……. And Captcha Breaking Experiment in PHP…. These terms now familiar to us. 1st one was made possible by Nadim vai and 2nd one by M. M. Rifat-Un-Nabi. Their post makes me inspire to get naughty once again more simply and more easily. Because I like simplicity ;). I also choosed SomeWhereInDhaka.Net Captcha to do this experiment.
The SomeWhereInDhaka.Net CAPTCHA suffers several weaknesses: fixed font face, fixed font size, no distortions and it’s easy to segment. In this experiment, I have developed simple algorithm to break the SomeWhereInDhaka.Net CAPTCHA.
- At first need the captcha image from the page, We can do it in two way :
(a) capturing only the captcha portion [I have used php function: imagejpeg()] or,
(b) capturing the page image by php function and then crop only captcha portion from that page.
- So, we got that captcha. Now sampling that captcha image
- Match sampling pattern with reference pattern. If matching is true then it will give output, In this case the captcha value. (No need any edit distance algorithm)
You can see the effect here.
I post my website ads 😛 as spam. So, isn’t it more simple.
And finally a sympathy will goes for SomeWhereInDhaka.Net. And also I would like to thanks them because they not change there captcha yet. and it help me to make this experiment :D. So, my friends if wana see weak captcha then what are you waiting for – just log in to SomeWhereInDhaka.Net and keep getting naughty :P.