Application Layer Firewalls operate at the:

A.
OSI protocol Layer seven, the Application Layer.

B.
OSI protocol Layer six, the Presentation Layer.

C.
OSI protocol Layer five, the Session Layer.

D.
OSI protocol Layer four, the Transport Layer.

Explanation:
Application layer firewall works at the application layer, which is layer 7 in the OSI model.
Incorrect Answers:
B: Application layer firewalls do not work at OSI layer 6, the presentation layer. They are at the Application
layer, layer 7.
C: Application layer firewalls do not work at OSI layer 5, the session layer. They are at the Application layer,
layer 7.
D: Application layer firewalls do not work at OSI layer 4, the session layer. They are at the Transport layer, layer
7.

https://en.wikipedia.org/wiki/Application_firewall