What is the most secure type of firewall?
A.
Packet Filter
B.
Stateful Firewall
C.
Circuit-level Proxy Firewall
D.
Application-layer Proxy Firewall
Explanation:
Answer D is correct; application-layer firewalls are the most secure: they have the ability to filter based on OSI layers three through seven.Incorrect Answers and Explanations: A, B, and C: Answers A, B, and C are incorrect. All are firewalls. A packet filter is the least secure of the four, due to the lack of state. A stateful firewall is more secure than a packet filter, but its decisions are limited to layers 3 and 4. Circuit-level proxy firewalls operate at layer 5, and cannot filter based on application-layer data.
Application-layer firewalls are the most secure: they have the ability to filter based on OSI layers three through seven.
This is debatable as per book Stateful Inspection is a third generation firewall unlike Application which is 2nd generation and it operates more efficiently that application level gateway.