Firewalking is a technique that can be used to gather information about a remote network
protected by a firewall. This technique can be used effectively to perform information gathering
attacks. In this technique, an attacker sends a crafted packet with a TTL value that is set to expire
one hop past the firewall. Which of the following are pre-requisites for an attacker to conduct
firewalking?
Each correct answer represents a complete solution. Choose all that apply.

A.
ICMP packets leaving the network should be allowed.

B.
An attacker should know the IP address of the last known gateway before the firewall.

C.
There should be a backdoor installed on the network.

D.
An attacker should know the IP address of a host located behind the firewall.

Explanation: