In a stateful inspection firewall, how are sessions monitored?

In a stateful inspection firewall, all packets in a session are analyzed to maintain a comprehensive understanding of the connection. This approach allows the firewall to track the state of active connections and apply security policies dynamically.

When a new connection is initiated, the firewall inspects the packets of that connection for compliance with security protocols. As the session continues, the stateful inspection process keeps track of the session’s state, ensuring that subsequent packets can be evaluated in the correct context. This not only helps in identifying legitimate packets belonging to an ongoing session but also provides a mechanism to detect attempts to inject malformed packets or conduct unauthorized activities within that session.

By monitoring all packets, the firewall can confirm that they adhere to the established characteristics of the session, enhancing security by preventing drops in communication continuity and mitigating risks from packet manipulation or spoofing. This capability differentiates stateful inspection firewalls from stateless ones, which only check the initial packet and are unable to track or analyze the ongoing session's state.