Abstract. In this paper we present an algorithm that is able to progressively discover nodes of a Skype overlay P2P network. Most notably, super nodes in the network core. Starting from a single, known Skype node, we can easily identify other Skype nodes in the network, through the analysis of widely available and standardized IPFIX (NetFlow) data. Instead of relying on the analysis of content characteristics or packet properties of the flow itself, we monitor connections of known Skype nodes in the network and then progressively discover the other nodes through the analysis of their mutual contacts.