Re: CAPTCHA image validation in web form

Couldn't you generate random placement and valid responses each time and store them on the server? So, boat may be in the first position the first time and then in the 4th position the second time, etc. With say, 15 images that were randomly chosen and named and placed on the page, say 5 at a time, you might be able to thwart a brute force attack.

Pete Helgren


Nathan Andelin wrote:

From Guillermo Andrades:
please select the image:
_ ICE _ BOAT _ GIRL _ THE MOON _ FLOWERS _ GUITAR _ THE SUN

The nice thing about that idea is that a bot with an OCR reader couldn't decipher an image of a boat, for example.

But there's a 1/7 chance that a bot could pick the right image the first time, and over a large enough number of iterations a smart bot could learn which radio button descriptions were paired with which image files. Over a large enough number of iterations a bot could esentially download & duplicate your entire image library and cross-reference table.

Nathan.