Re: CAPTCHA image validation in web form

Nathan Andelin wrote:

If one does go through the effort of assembling and cataloging an image library, one thing that may help would be to use photoshop filters (or something comparable) to generate a lot of different image files of the same subject - like a cat with varying colors, opacity, and so forth that wouldn't be any problem for humans, but make it harder for a bot author to obtain a signature on the image.

Or you could do what I suggested a dozen posts ago and use a servlet to serve the image, giving you the ultimate ability to randomize the image at runtime.

This clearly shows what I meant by "diminishing returns". It's also the underlying truth to the phrase "the perfect is the enemy of the good". You can stop 99% of the hackers with a fairly simple solution. You can spend ten times more and stop 99.9% of them. You can continue down that path and stop 99.9999% of the hackers, but at what cost?

Joe