If you do run an NTP server, please make sure it's not vulnerable to DDoS amplification (monlist, readvar, etc need to be disabled) and apply some rate limiting to make it less useful for reflection attacks. And be proactive about monitoring its traffic volume.
If you see high packet rate from a specific IP address or prefix, it's very likely not them abusing your service, but rather you attacking them by responding to spoofed requests.
If you see high packet rate from a specific IP address or prefix, it's very likely not them abusing your service, but rather you attacking them by responding to spoofed requests.