Interesting paper from IsecLab (Institute Eurécom, University of California Santa Barbara, Ruhr University Bochum, Northeastern University): “The Underground Economy of Spam: A Botmaster’s Perspective of Coordinating Large-Scale Spam Campaigns”.

Based on the value of the products and services that we previously described, we can estimate on a high level the cost of operating Cutwail’s spam campaigns, and approximate the transaction volume related to such an operation. As we discussed in Section 3, there were an average of 121,336 unique IPs online per day. Thus, the Cutwail operators may have paid between $1,500 and $15,000 on a recurring basis to grow and maintain their botnet (assuming they did not develop their own loads system). If we estimate the value of the largest email address list (containing over 1,596,093,833 unique records) from advertised prices, it is worth approximately $10,000–$20,000. Finally, we estimate the Cutwail gang’s profit for providing spam services at roughly $1.7 million to $4.2 million since June 2009 (contingent on whether bulk discounts were provided to customers).