The attack described is a DNS amplification attack. It involves infected endpoints sending DNS requests with spoofed IP addresses to external DNS servers. The DNS servers then send large responses to the spoofed addresses, which are actually the targets of the attack. This can result in a significant amount of traffic being directed at the target, overwhelming their network resources. DNS amplification is a type of Distributed Denial of Service (DDoS) attack that leverages the DNS protocol to amplify the attack traffic.