A network technician is concerned that an attacker is attempting to penetrate the network, and
wants to set a rule on the firewall to prevent the attacker from learning which IP addresses are
valid on the network. Which of the following protocols needs to be denied?
A.
TCP
B.
SMTP
C.
ICMP
D.
ARP
Explanation:
The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet Protocol
Suite. It is used by network devices, like routers, to send error messages indicating, for example,
that a requested service is not available or that a host or router could not be reached. ICMP can
also be used to relay query messages. It is assigned protocol number 1.