The computer science division of the University of California at Berkeley (UC-Berkeley) has studied Internet crime and published several papers describing how it is done and how they derive profits from it. Of particular interest is the Bibliography of some of these papers which give us links to other studies and reports with descriptions of how we are targeted by criminal gangs.
As publishers involved in the Adsense program these papers can be enlightening.
The first one that I encountered was a description of two modern click-fraud schemes which take advantage of the ease of penetration of PCs and the conversion of the PCs into botnets under the supervision of Command and Control servers to find specific ads, click on them, and produce profits for their controllers. [icsi.berkeley.edu
I found the next link in the Bibliography of the Berkeley study (which contains numerous gems) This link is to a Canadian report on how a modern international criminal enterprise uses its access to the Internet to capture millions of dollars in profits. [infowar-monitor.net
The first link is directly related to problems publishers are having right now. The second link describes how easy the process can be and how seldom Internet crime is punished.
Well worth reading! There is a lot of this stuff out there.