A system and method for spammer host detection from network flow data profiles comprises constructing one or more cluster profiles and detecting spammer hosts. Construction cluster profiles comprises observing network flow data from one or more hosts; for each host, representing the network flow data associated with the host as a multidimensional vector; clustering the vectors of the hosts into the plurality of cluster profiles; annotating each cluster profile using at least one of black lists and white lists; and calculating a confidence in each cluster profile annotation. Detecting spammer hosts comprises observing the network flow data from a new host; representing the network flow data associated with the new host as a multidimensional vector, and placing the new multidimensional vector of the new host into one cluster profile of the one or more cluster profiles.