CAPTCHA breaking

[h9uest]

Hi all:

Probably this is not so related with C++ since one can do the job with any other language. However, my experience with this forum is people are generally helpful and knowledgeable, so I'd like to try my luck.

Here's the thing:
I intend to do my thesis on machine learning attacks against an photo-based captcha system. An ideal target looks like vidoop but doesn't have to be vidoop. Essentially, the systems I'm interested in have a mapping from word term to photo.

Can anyone share with me any photo-based captcha system that allows me to use it as the test? In fact, I only need the collection of photos used by the captcha system. I know there're plenty of photos on the web if I want to build a test captcha system by myself, but you know, for academic purpose, it's always good to validate your approach on a real world system instead of making up one.

Thanks for any ideas.

[h9uest]

To clarify:

I don't want captcha systems like the reCaptcha, which is essentially text based captcha system.
Also, I don't want ASIRRA. That's too specific about animals.

Vidoop is pretty much ideal, but it has gone out of business. sigh ... :(