Network security and mysterious connections to Yun

Official Hardware Classic Yún
1

As a total n00b to network security, I was alarmed to check the "Realtime Connections" tab in the advanced configuration menu and find that my little Arduino is apparently connecting to sometimes as many as 20 computers, several of which are outside my local network. It seems to be sending one packet to mysterious IPs such as li506-17.members.linode.com:123, host2.kingrst.com:123, va-time.techprogress.org:123 etc via UDP. Can anyone shed some light on either why I shouldn't worry about this or what I can do to prevent it?

I'd like to be able to leave (and log into myself) a Yun-based device at a client's house working as a data logging controller for heating systems without having to worry about compromising their network's security.

2

You may feel safe. Port 123 is used by NTP [0], network time protocol. It's your yun keeping its internal clock up to date.

[0] http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt

3

Thanks a lot. For now I guess I just won't worry about why it has to send a packet to so many different places to update its clock.