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ABSTRACT

Skype applies strong encryption to provide secure communication inside the whole Skype network. The communication ports of clients are chosen randomly. As a consequence, traditional port based or payload based identification of Skype traffic cannot be applied. In this paper we present a novel flow dynamics based identification method to discover both Skype hosts and voice calls. The method is based only on packet headers and extracted flow level information. This method is the second algorithm from our research. It has a significant improvement over our first method [1]. It can detect the randomly selected communication port of the Skype client, which makes the identification more reliable. The whole identification process is scripted in Transact-SQL, thus it can be executed automatically. We also present the validation of the new algorithm together with the analysis of the identification results.

REFERENCES

• 1: M. Perényi, A. Gefferth, T. Dinh Dang, S. Molnár, "Skype Traffic Identification", accepted to GLOBECOM 2007 and based on the downloadable technical report: M. Perényi et al. Identification and Analysis of Skype Traffic, http://yossarian.tmit.bme.hu/download/techrep.doc
• 2: Fabrice Desclaux, "Skype uncovered -- Security study of Skype", EADS, 2005
• 3: S. Ehlert, S. Petgang, "Analysis and Signature of Skype VoIP Session Traffic", Technical Report NGNI-SKYPE-06b, Fraunhofer FOKUS, Berlin, Germany
• 4: W. Ghandour, "Blocking Skype Using Squid and OpenBSD", Help Net Security (www.net-security.org), 2005
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• 7: Kuan-Ta Chen , Chun-Ying Huang , Polly Huang , Chin-Laung Lei, Quantifying Skype user satisfaction, Proceedings of the 2006 conference on Applications, technologies, architectures, and protocols for computer communications, September 11-15, 2006, Pisa, Italy
• 8: Skype Technologies S. A., "Skype - Guide for Network Administrators Version 1.01", 2005, http://www.skype.com/security/guide-for-network-admins.pdf
• 9: P. Biondi, F. Desclaux, "Silver needle in the Skype", EADS, 2006
• 10: S. A. Baset, H. Schulzrinne, "An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol", in Proc. of INFOCOM'06, Barcelona, Spain, 2006
• 11: B. W. Wah, B. Sat, M. Gannon, "Analysis and Evaluation of the Skype and Google-Talk VoIP Systems", Multimedia and Expo 2006, Toronto, Canada, 2006
• 12: T. Dinh Dang, M. Perényi, A. Gefferth, S. Molnár, "On the Identification and Analysis of P2P Traffic aggregation", in Proc. of Networking 2006, Coimbra, Portugal, 2006

INDEX TERMS

Keywords:
Skype, analysis, traffic identification