First results of the NorNet-based security research project on SIP (i.e. Voice over SIP telephony) attacks in the Internet, performed at the University of Duisburg-Essen, is going to be presented at the IFIP Networking 2014 in June in Trondheim. By gaining insight into attack strategies with the help of NorNet, new countermeasures may be developed that finally make the Internet and Voice over IP communications more secure.
Also have a look at the paper «A Distributed Infrastructure to Analyse SIP Attacks in the Internet» with the results! The project homepage can be found here.