er categorized, according to the different parts of SIP messages that could be used. These are: (a) a message's headers, © 2009 by Taylor & Francis Group, LLC SIP Vulnerabilities for SPIT, SPIT Identification Criteria (b) a message's body, and (c) the reason phrases of a message. In addition, we have identified three possible types of SPIT that could be injected in a SIP message, namely: (a) text SPIT injected in a header field, (b) media SPIT carried in the message body, and (c) hyperlink SPIT injected in a header field. Tables 19.2 through 19.4 depict the specific SIP header fields that can be used for a detailed semantic analysis, SO as to detect a SPIT call or message alongside with the type of the SPIT that could be sent. Table 19.3 presents the type of messages containing a body, which could be used in order to make a SPIT call (or message). They are categorised in terms of request and response messages. SPIT contained in the message body can be text, media or hyperlink. TABLE 19.2 SIP Headers That Could Be Used for SPIT Request Response Header fields SPIT type messages messages Subject Call-Info Hyperlink Contact Retry After Alert-Info Hyperlink REPLY TO Error-Info Hyperlink Warning Header fields related to SIP messages' bodies (not carrying SPIT "directly") Content-Disposition Displayed message body Content-Type Displayed message body TABLE 19.3 Request-Response Messages That Could Be Used for SPIT INVITE Request messages 180 Ringing 183 Session Progress 200 OK Response messages 300 Multiple Choices 380 Alternative Service 488 Not Acceptable Here 606 Not Acceptable © 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security TABLE 19.4 Reason Phrases That Could Be Used for SPIT 182 Queued 183 Session Progress 200 OK 400 Bad Request 480 Temporarily Unavailable 484 Address Incomplete Table 19.4 presents the reason phrases of response messages that could be used for SPIT purposes. Reason phrases may contain text or hyperlink type of SPIT. 19.4.2 SIP User Agent Criteria These crite