Definition: Stateful Inspection is a more in-depth form of Packet Filter firewall. While a Packet Filter only checks the packet header to determine the source and destination address and the source and destination ports to verify against its rules, Stateful Inspection checks the packet all the way to the Application Layer. Stateful Inspection monitors incoming and outgoing packets to determine not only source and destination, but also context. By ensuring that only requested information is allowed back in Stateful Inspection helps protect against hacker techniques such as IP spoofing and port scanning.
Also Known As: Dynamic Packet Filter