Why would an ethical hacker use the technique of firewalking?

A.
It is a technique used to discover wireless network on foot.

B.
It is a technique used to map routers on a network link.

C.
It is a technique used to discover the nature of rules configured on a gateway.

D.
It is a technique used to discover interfaces in promiscuous mode.

Explanation:
Firewalking uses a traceroute-like IP packet analysis to determine whether or not a particular packet can pass from the attacker’s host to a destination host through a packet-filtering device. This technique can be used to map `open’ or `pass through’ ports on a gateway. More over, it can determine whether packets with various control information can pass through a given gateway.