Who do these OwnTracks devices belong to?!

I’ve just looked at my OwnTracks integration (which has been up and running fine for a while) and suddenly I see 6 strange device_trackers that do not belong to me.

Currently I’m using Home Assistant in a Docker Container and accessing it remotely through the Nabu Casa Home Assistant Cloud.

Can others see my device_trackers too? How do I get rid of them and how do I ensure my data isn’t exposed somewhere disparate?