As with any other emerging system, the analysis of the security of Peer-to-Peer Session Initiation Protocol systems is of crucial importance for its secure development and future standardization. In this survey, we analyze the security of these systems by studying the attacks that can be launched against them. After an overview of the services that conform its architecture (access control, bootstrap, routing, storage and communication) we present the different attacks that can be launched against each of the services described. Also, for each presented attack, we review the defense mechanisms that can be used to prevent the attack, summarizing their advantages and drawbacks. This analysis presents a clear picture of the new security challenges which must be considered for the development of a Peer-to-Peer Session Initialization Protocol system and a revision of the security mechanisms that can be used to secure them.