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