Hi The following would probably be illegal so do not actually do this. But what if... there are just 4 billion IPv4 addresses. Scanning that address-space for open NTP is trivially done in a few hours. Abusing these servers for reflection attack is as trivial, hence the problem. How can we get the responsible parties to fix their NTP servers? Answer: DDoS them. With their own service. Or it could be a DDoS defense. As a victim of an ongoing NTP reflection attack, you know exactly the IP-addresses of the vulnerable NTP servers used to attack you. Make them stop by sending back forged NTP packets, so they use up their available bandwidth to DDoS each other instead of you. This could even be automated. If you let them attack their next-hop as discovered by traceroute, it might not even be illegal or harmful. They will only bring down their own link, do no more harm to the internet at large and they can fix it by stopping the NTP service. If they are part of an ongoing DDoS attack it is just self defence to shut them down in the least harmful way possible. Regards, Baldur