GENERATING HARD INSTANCES OF CAPTCHAS
First Claim
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1. A computer-implemented method for modifying a set of captchas based on responses to the captchas from one or more client computers, comprising:
- classifying first ones of the responses as coming from an automated process and second ones of the responses as coming from a human;
modifying a first one of the captchas for which the first responses represent a corresponding success rate higher than a first threshold; and
eliminating a second one of the captchas from the set of captchas for which the second responses represent a corresponding failure rate above a second threshold.
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Abstract
Methods and systems are described for enhancing the difficulty of captchas and enlarging a core of available captchas that are hard for an automated or robotic user to crack.
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Citations
12 Claims
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1. A computer-implemented method for modifying a set of captchas based on responses to the captchas from one or more client computers, comprising:
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classifying first ones of the responses as coming from an automated process and second ones of the responses as coming from a human; modifying a first one of the captchas for which the first responses represent a corresponding success rate higher than a first threshold; and eliminating a second one of the captchas from the set of captchas for which the second responses represent a corresponding failure rate above a second threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A computer system for selectively accepting access requests to a service, the computer system configured to:
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determine a hard set of captchas from a plurality of possible captchas; render some or all of the hard set of captchas on a computing device; receive responses to the rendered hard set of captchas; track the received responses to the rendered hard set of captchas; distinguish between responses believed to be entered by a human and responses believed to be entered by an automated client; and eliminate a group of the hard set of captchas, the eliminated group having a failure rate of response above an acceptable threshold for those responses believed to be entered by a human. - View Dependent Claims (8, 9, 10)
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11. A computer-implemented method for selectively accepting access requests from a client computer connected to a server computer, comprising:
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presenting a plurality of captchas to a plurality of users wishing to access a service; receiving answers to the captchas; monitoring registration for the service by a user and determining if registration characteristics of the user are correlated with characteristics of a robotic user; monitoring the post registration use of the service by a user and determining if post registration usage characteristics of the user are correlated with usage characteristics of a robotic user; assessing the answers to the captchas and tracking correct and incorrect of the answers; and classifying the captchas that receive incorrect answers from a suspected robotic user for inclusion in a hard set.
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12. A computer-implemented method, comprising:
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causing an original set of captchas to be rendered on a first plurality of client computers; and causing a modified set of captchas to be rendered on a second plurality of client computers, the modified set of captchas including a modified captcha corresponding to a first captcha from the original set of captchas, the modified captcha having been modified as a result of responses to the first captcha by automated processes, the modified captcha being more difficult for the automated processes to successfully process.
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Specification