Which of the following is a denial of service attack that attempts to overwhelm a target with ICMP echo requests?

A Smurf attack also leverages ICMP but uses a spoofed source IP and broadcasts to an amplification network so that many third-party hosts reply to the victim - it is an amplification/reflection attack, not a direct ICMP flood.

A ping flood (ICMP flood) works by sending as many ICMP echo request packets as possible directly to a target host, consuming its inbound bandwidth and CPU cycles processing replies. The sheer volume of traffic prevents the target from servicing legitimate requests, achieving denial of service through resource exhaustion rather than exploitation of a vulnerability.

The Ping of Death sends a single deliberately malformed or oversized ICMP packet designed to crash or destabilize the target's IP stack, relying on a parsing vulnerability rather than traffic volume.

A SYN flood exploits the TCP three-way handshake by sending large numbers of SYN packets without completing connections, exhausting server connection state tables - it uses TCP, not ICMP.