DNS Flood (NXDOMAIN Flood) is a type of cyber attack that targets the Domain Name System (DNS) infrastructure of an organization. This attack is designed to overwhelm the DNS servers with a large volume of requests, making it difficult for them to respond to legitimate requests.

The NXDOMAIN Flood specifically targets non-existent domain names, also known as NXDOMAIN, by sending many requests for non-existent domain names to the DNS server. The server then responds with an error message indicating that the domain name does not exist, which generates additional traffic and further exacerbates the attack.