This paper studies an active underground economy which specializes in the commoditization of activities such as credit card fraud, identity theft, spamming, phishing, online credential theft, and the sale of compromised hosts. Using a seven month trace of logs collected from an active underground market operating on public Internet chat networks, we measure how the shift from “hacking for fun” to “hacking for profit” has given birth to a societal substrate mature enough to steal wealth into the millions of dollars in less than one year. Categories and Subject Descriptors K.4.1 [Public Policy Issues]: ABUSE AND CRIME INVOLVING COMPUTERS General Terms Measurement,Security Keywords eCrime, Underground Markets ∗This research was supported in part by CyLab at Carnegie Mellon under grant DAAD19-02-1-0389 from the Army Research Office, and grants CNS-0537246, CCF-0424422, CNS-0433668, and NSF-0433702 from the National Science Foundation. Jason Franklin performed this research whi...