First lets clarify what is Nslookup – it is a powerful network administration command-line tool, available for many of the popular computer operating systems for querying Domain Name System (DNS) to obtain domain names or IP addresses, mapping or for any other specific DNS Records.
These attacks usually use the UDP protocol. It is a simple connectionless communication model with a minimum of protocol mechanism. This means that one of the sides in the communication can send large amount to the other without restrictions. Without any confirmation and it doesn’t matter if the second side receive the data.
Due to the way the UDP protocol works, cyber-criminals use it to generate DDoS amplification attacks. The attacker sends a small UDP request with a spoofed IP address of the victim to public services.
The UDP protocol doesn’t require a connection verification between the parties. This is why the public services reply with the requested data to the IP address of the victim. As bigger is the data returned by exploited public service, bigger is the DDoS amplification factor.