I have selected two files using OneSwarm search, that is, two torrents that I expect are not public torrents because I found them using OneSwarm. I notice that one shows a tracker URL of
http://tracker.not.needed.invalid/announce
while the other shows
http://tracker.openbittorrent.com/announce
This second looks like I'm using a public bittorrent tracker, although I currently show a connection error for it. I certainly do not want to be using a public tracker, so I'm interested in what this means.