1. A system for classifying flows of communication packets from a network, the system comprising: a classification processor that receives unclassified input flows of communication packets from a front-end processor and assigns a classification to a given unclassified input flow that indicates whether the input flow is to be analyzed by a flow analysis processor, wherein the classification is assigned by the classification processor based on less than 5% of the input packets of the given input flow, wherein the classification processor assigns a first classification to a first unclassified input flow that indicates whether the first flow is to be analyzed by the flow analysis processor based on information produced in assigning a second classification to a second unclassified input flow, and wherein the classification processor identifies a server-side address and a client-side address in the second input flow, and uses the identified server-side and client-side addresses in assignment of the first classification to the first input flow.