Final answer:
A Smurf attack utilizes the Internet Control Message Protocol (ICMP) to flood a target system with traffic, resulting in a denial of service. The correct protocol associated with a Smurf attack is ICMP (Option D).
Step-by-step explanation:
The Smurf attack is a type of distributed network denial-of-service (DDoS) attack that exploits the Internet Control Message Protocol (ICMP) to flood a target system with traffic. When a Smurf attack occurs, the attacker sends ICMP packets, which are usually used for diagnostics such as echo requests (ping), to network broadcast addresses from a spoofed IP address that is actually the victim's address. This results in the network's devices responding to the echo request and in turn flooding the victim with replies, causing a denial of service situation.
By answering the student's question directly: the protocol used in a Smurf attack to conduct the attack is D. ICMP.