Abstract: In one example embodiment, a server obtains network flow metadata of a network flow of a host in a network. The server identifies one or more attributes of the network flow metadata. For each host group of a plurality of host groups, the server determines whether the one or more attributes of the network flow metadata satisfy one or more criteria for the host group. For each host group for which it is determined that the one or more attributes of the network flow metadata satisfy the one or more criteria, the server classifies the host as belonging to the host group.