2. Protection system for SIP protocol

SIP is a transactional protocol in which each transaction consists of a request and at least one response. An attacker will usually use a malformed message in a transaction or sequence of transactions to compromise a SIP device. They may also use a syntactically well-formed and semantically correct message to interrupt or cleanly terminate a session in progress between two or more users. A protection system must therefore be capable of protecting SIP equipment from malicious messages, whether malformed or not.

From a functional point of view, a protection system for the SIP protocol is either proactive or reactive. A proactive system prevents malicious messages, transactions or dialogs from reaching victims. Such a system can be implemented via a stateful model, whose role is to record the states, objects and messages of the SIP protocol during its activities, which...