VoIP SPAM and a Defence against this Type of Threat

摘要

This paper deals with VoIP Spam and various techniques of defence against this threat. First of all we gave attention to the security in IP telephony and we divided the threats in several categories according to their specific behaviour and their impact on the affected system. Then we focused our work on Spam over Internet Telephony (SPIT) as a real threat for the future. We have developed both a tool generating SPIT attacks and AntiSPIT tool defending communication systems against SPIT attacks. AntiSPIT is based on our new approach evaluating call detail records and can be easily implemented to any communication system. AntiSPIT represents an effective protection based on statistical blacklist and works without participation of the called party which is a significant advantage. We implemented our method into Asterisk under GNU general public license.