Which type of firewall can act on the behalf of the end device?

Which type of firewall can act on the behalf of the end device?
A . Stateful packet
B . Application
C . Packet
D . Proxy

Answer: D

Explanation:

Application firewalls, as indicated by the name, work at Layer 7, or the application layer of the OSI model.

These devices act on behalf of a client (aka proxy) for requested services.

Because application/proxy firewalls act on behalf of a client, they provide an additional "buffer" from port scans, application attacks, and so on. For example, if an attacker found a vulnerability in an application, the attacker would have to compromise the application/proxy firewall before attacking devices behind the firewall. The application/proxy firewall can also be patched quickly in the event that a vulnerability is discovered. The same may not hold true for patching all the internal devices.

Source: http://www.networkworld.com/article/2255950/lan-wan/chapter-1–types-of-firewalls.html