Which of the following firewalls inspects the actual contents of packets?

A.
Packet filtering firewall

B.
Application-level firewall

C.
Circuit-level firewall

D.
Stateful inspection firewall

Explanation:

The application level firewall inspects the contents of packets, rather than the source/destination or
connection between the two. An Application level firewall operates at the application layer of the
OSI model.
Answer option C is incorrect. The circuit-level firewall regulates traffic based on whether or not a
trusted connection has been established. It operates at the session layer of the OSI model.
Answer option A is incorrect. The packet filtering firewall filters traffic based on the headers. It
operates at the network layer of the OSI model.
Answer option D is incorrect. The stateful inspection firewall assures the connection between the
two parties is valid and inspects packets from this connection to assure the packets are not
malicious.
Reference: “http://en.wikipedia.org/wiki/Firewall_(networking)#Third_generation_-
_application_layer”