Let's say I have a ton of credit card usage data and have also some means to predict if a given transaction is fraudulent. Now I want to know what kind of criminal entities are behind these frauds. Maybe some are big international/domestic crime organizations, some are small groups and some are individuals etc.
I'd assume that cluster analysis would help making the first step in this situation. What combination of techniques are useful in this scenario, and how do you apply them?
EDIT: To clarify, what I want to do is clustering "similar" fraudulent transactions so that I can make some guess on from whom/what they originated. Maybe certain types of frauds tend to come from a certain region. Some other types target certain combinations of flaw in the system (e.g. lot of small transactions vs. bigger transactions) etc. In principle, I want to extract some pattern that will help the investigators.