A Model for Spam Prevention in IP Telephony Networks using Anonymous Verifying Authorities

Unsolicited emails, more commonly known as spam, have plagued the use and efficiency of email since its inception. With the introduction of ungoverned cheap voice communications, such as IP telephony, spam over telephony (SPIT) and its prevention is set to dominate and drive whether the technology is widely adopted or not. A possible example of voice spam schemes includes the use of Interactive Voice Response (IVR) systems in conjunction with automated telemarketing sales to repeatedly initiate call setups and fill voicemail boxes. The problem faced is to design a system that allows legitimate voice call establishment while anonymously blocking unwelcome ones. An anonymous approach prevents voice spam by prohibiting spammers from establishing call and do not call lists. In this paper we propose a new model as an extension to a call signalling phase (or call setup phase) as a means to prevent unwanted voice spam. In doing so we define a IP telephony “call me back” scheme using an Anonymous Verifying Authority (AVA) and Mediator in blocking unsolicited voice calls. We illustrate the use of a “call me back” request in allowing the callee to accept or reject the call. Verification may be based on the callee’s personal call policy thus filtering unsolicited voice spam.