An ICMP flood attack is also known as a ping attack in which attackers send a large number of ICMP ping packets to a DNS server repeatedly in order to hinder the server's ability to respond to other requests. It can also be an attempt to send a large number of ping packets to the broadcast IP of a subnetwork, otherwise known as a Smurf attack, as a basic means of amplifying an attack across more hosts than a normal ping would typically permit. These types of attacks can be dealt with by setting a policy to disallow pings to the broadcast IP on the network.
Note: When threat protection is enabled, ICMP ping size (for IPv4 and IPv6) is limited to 16,000 bytes.