I assure you that I know enough to at least hold an intelligent conversation on mobile security. On iOS there is no "system level messaging component". (i)Messages are stored in a SQLite database that is protected via entitlements and sandboxing; the Messages app is given the ability to access it legitimately. Attackers can either exploit the Messages itself and (via code execution in that process) grab a user's messages, or they can exploit something else (such as the web content process) and then escalate privileges from there to bypass the sandbox.