Large financial and telecommunication networks provide a rich source of problems for the data mining community. The problems are inherently quite distinct from traditional data mining in that the data records, representing transactions between pairs of entities, are not independent. Indeed, it is often the linkages between entities that are of primary interest. A second factor, network dynamics, induces further challenges as new nodes and edges are introduced through time while old edges and nodes disappear.

We discuss our approach to representing and mining large sparse graphs. Several applications in telecommunications fraud detection are used to illustrate the benefits of our approach.