A system, method, and device for classifying traffic is disclosed. The method includes (i) correlating a plurality of network traffic sessions with same source indicators to obtain correlated network traffic, (ii) classifying the plurality of network traffic sessions based at least in part on a plurality of first-layer classifiers to obtain a set of first-layer classifications, wherein the plurality of first-layer classifiers are respectively associated with a plurality of protocols, and (iii) determining a second-layer classification for the correlated network traffic based at least in part on the set of first-layer classifications.