Discovering communication traffic in a computer network is useful to administrators of computer networks. Communication packets from a communication transaction on the network are read to determine a source computing device and to determine whether the communication transaction contains a data pattern match to one of a plurality of defined data patterns. If a match is made to an exact data pattern, the source computing device is associated with an application or service corresponding to that exact data pattern. If a match is made to a statistical data pattern, the source computing device is associated with an application or service corresponding to that statistical data pattern if a threshold number of data pattern matches have occurred for that statistical data pattern for the source computing device.