SPITters are able to locate accessible third-party SIP servers by using free available automated tools. By relaying instant messages or calls through sev- eral open relay SIP proxies at the same time, it is possible to flood the SIP network with large amounts of SPIT calls in a very short time before being detected. The problem generated by using open relays can be addressed on the one side by forcing the SIP users to utilize their outgoing proxies and on the other side by enhancing security between the different providers. 23.3.3 Automated SPIT There are hardware or software that generate calls and send messages auto- matically. Any SIP client that can be configured to generate a huge number of simultaneous calls can be used for this purpose. The SIP client SIPp [16] is a good example of these automats. These automats may be used alone or with other equipment such as Interactive Voice Response (IVR) to deliver pre-recorded voice messages to the chosen recipients. Let us mention that an efficient way to deal with the SPIT automat problem is to use any mechanism that challenges the SIP request sender as automats will certainly fail to answer correctly to the challenges. Another mechanism is C 2009 by Taylor & Francis Group, LLC A Conceptual Architecture for SPIT Mitigation to analyze the audio stream generated by an audio file that a SPITter wants to relay over once the SIP session is established. This will be discussed later. 23.3.4 Human SPITters Telemarketing is a method for advertising products and offering services. It is usual that companies and organizations use professional telemarketers or call centers to make phone calls and send messages to potential customers on their behalf. The phone calls here could be PSTN or VoIP based. We mentioned previously that PSTN was the main tool used by spammers to carry out their activities and VoIP was the potential carrier for spam in the future because of the convergence of voice and data provided by this technology. Although, this spam category (generated by human be