Which firewall type below uses a dynamic state table to inspect the
content of packets?

A.
An application-level firewall

B.
A stateful-inspection firewall

C.
A circuit-level firewall

D.
A packet-filtering firewall

Explanation:
A stateful-inspection firewall intercepts incoming packets at the Network
level, then uses an Inspection Engine to extract state-related information
from upper layers. It maintains the information in a dynamic
state table and evaluates subsequent connection attempts.
* packet-filtering firewall is the simplest type of firewall commonly
implemented on routers. It operates at the Network layer and offers
good performance but is the least secure.
* application-level firewall or application-layer gateway, is more secure because it examines the
packet at the application layer, but at the expense of performance.
* circuit-level firewall, is similar to the application-level firewall in that it functions as a proxy server,
but differs in that special proxy application software is not needed. Sources: Hacker Proof by Lars
Klander (Jamsa Press, 1997) and Checkpoint Firewall-1 Stateful Inspection
Technology (www.checkpoint.com).