Technology Review covered a CAPTCHA paper from computer scientists at UC San Diego that was presented last week at the 2010 USENIX Security Symposium.
The paper: "Re: CAPTCHAs -- Understanding CAPTCHA-Solving from an Economic Context," Marti Motoyama, Kirill Levchenko, Chris Kanich, Damon McCoy, Geoffrey M. Voelker, and Stefan Savage, Proceedings of the USENIX Security Symposium, Washington, D.C., August 2010.
The abstract is below. The Technology Review story by Christopher Mims is here.
Reverse Turing tests, or CAPTCHAs, have become an ubiquitous defense used to protect open Web resources from being exploited at scale. An effective CAPTCHA resists existing mechanistic software solving, yet can be solved with high probability by a human being. In response, a robust solving ecosystem has emerged, reselling both automated solving technology and realtime human labor to bypass these protections. Thus, CAPTCHAs can increasingly be understood and evaluated in purely economic terms; the market price of a solution vs the monetizable value of the asset being protected.We examine the market-side of this question in depth, analyzing the behavior and dynamics of CAPTCHA-solving service providers, their price performance, and the underlying labor markets driving this economy.
