Which of the following firewall types inspects Ethernet traffic at the MOST levels of the OSI model?
Packet Filter Firewall
Stateful inspections occur at all levels of the network.
A: Packet-filtering firewalls operate at the Network layer (Layer 3) and the Transport layer (Layer 4) of the Open
Systems Interconnect (OSI) model.
C: The proxy function can occur at either the application level or the circuit level.
D: Application Firewalls operate at the Application layer (Layer7) of the OSI model.
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis, 2014,
Stewart, James Michael, CompTIA Security+ Review Guide, Sybex, Indianapolis, 2014, p. 6