In a UDP attack, the targeted system is forced to reply to the UDP packets with ICMP Destination Unreachable packets, eventually leading the target system becomes unreachable to other clients. The targeted system responds to a UDP flood by:
The attacker may also spoof the IP address of the UDP packets, ensuring that the excessive ICMP return packets do not reach them, and anonymize their network location.
Refer to Configuring use case 4 - protection against UDP flood attacks.