Hacker attacks against SIP-based VoIP networks have been rare but as the use of the protocol grows and extends to other types of multimedia interaction, attacks will become more prevalent and potentially slow the growth of this technology. Service providers must work with standards bodies, equipment suppliers and customers to develop and deploy defenses.     

Currently most SIP usage simply provides a less expensive way to link an enterprise's phones to the public switched telephone network (PSTN) or provides an interconnect to an enterprise's remote offices. But as SIP providers interconnect with each other to provide purely digital paths that never touch the PSTN, the danger of hacker attacks is increasing.