Don't know if this has been talked about here:
http://facility.unavco.org/kb/questions/800/
Hmmm....
NTP Amplification Flaw To Blame For Gaming DDoS Attacks | Threatpost
Our immediate recommendation is that any new-generation JAVAD or Trimble NetR5, NetR8, or NetR9 GNSS receiver that has a direct connection to the internet - i.e. a public IP address with no firewall router, cellular modem or VSAT/BGAN in its communication path - should have its NTP server disabled and/or IP Filtering enabled as soon as possible.
NTP servers are left enabled by default on these devices although only a small minority of users require this functionality.
The server can be disabled in the "Network Configuration -> NTP" tab of a Trimble NetR5, NetR8, or NetR9 on the web interface. The recommended configuration will be: