Overview
An APIDS will monitor the dynamic behavior and state of the protocol and will typically consist of a system or agent that would typically sit between a process, or group of servers, monitoring and analyzing the application protocol between two connected devices.
A typical place for an APIDS would be between a web server and the database management system, monitoring the SQL protocol specific to the middleware/business logic as it interacts with the database.
Read more about this topic: Application Protocol-based Intrusion Detection System