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[Asrg] Suggested change to FUSSP CAPTCHA rule, or: using bounces to attack CAPTCHA systems

2005-01-09 02:50:13
Michael Kaplan said,

> I suggest that the following be removed from the FUSSP list:
> "Spammers can't automate puzzle solving, character recognition,
> or or other hoops in the FUSSP that legitimate users must jump
> manually."

I object; Michael, you did not provide, imho, sufficient empirical or other convincing evidence, proving that your CAPTCHA is immune to automated solution. I understand your intuitive claims but I think these can only serve as some intuition. Of course, such intuition could convince somebody to use your system, and after 10-20 years of such serious use, you may claim you have a convincing proof.

On the other hand... Did you consider that user used to receiving and solving your CAPTCHA in bounces to their e-mail, may be abused by spamware or other malware, causing them to solve your CAPTCHAs for the hacker's advantage? I mean, these poor fellows whose machines are zombies, now will become victims on their human time as well, as they are forced to solve your CAPTCHA's... Of course, the spamware will present the CAPTCHAs as if they are bounces to mail that the user actually sent - this is trivial (certainly with your current design - I guess, one response would be to incorporate some aspects of the e-mail into the CAPTCHA itself - not that this solves the entire problem...)

So I suggest adding/modifing the rule as follows:
"Spammers can't automate puzzle solving, character recognition,
or or other hoops in the FUSSP that legitimate users must jump manually, and can't trick users into solving these puzzles for them."

Best, Amir Herzberg
http://AmirHerzberg.com


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