Stateful Inspection Firewall

Definition:

• A stateful inspection firewall, also known as a dynamic packet filtering firewall, monitors the state of active connections and makes decisions based on the context of the traffic. It maintains a state table that tracks the state and characteristics of each connection.

How It Works:

• Stateful Filtering: Examines packets in the context of the traffic flow, maintaining state information about active connections.
• State Table: Keeps track of each active connection’s state, including source and destination IP addresses, port numbers, sequence numbers, and flags.
• Inspection of Multiple Layers: Analyzes information at multiple layers, including the network layer and transport layer, and sometimes application layer.

Features:

• Stateful: Maintains state information, allowing it to make more informed decisions based on the context of the traffic.
• Enhanced Security: Can detect and block more sophisticated attacks, such as session hijacking and certain types of DoS attacks.
• Dynamic Rules: Automatically updates filtering rules based on the state of active connections.

Limitations:

• Complexity: More complex to configure and manage due to its advanced features and state tracking.
• Performance Overhead: Generally slower than packet filtering routers due to the additional processing required to maintain and inspect connection states.
• Resource Intensive: Requires more memory and processing power to maintain the state table and perform deep inspections.

Example Use Case:

• Ideal for larger networks or environments that require robust security measures, such as enterprises and data centers.