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US 2010/0077209 A1Published application
Generating hard instances of captchas
AssigneeYahoo! Inc.
InventorsAndrei BRODER, Shanmugasundaram RAVIKUMAR
Life of this patent
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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.
Claims12
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.
1 more element
A computer system for selectively accepting access requests to a service, the computer system configured to:
- 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.
4 more elements
A computer-implemented method for selectively accepting access requests from a client computer connected to a server computer, comprising:
- 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.
4 more elements
A computer-implemented method, comprising:
- 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.
Dependencies are inferred from the claim text.