I notice that Network Scanner is "Probing", i.e. it is trying to scan all IPv4 ranges starting at 0.0.0.0. It looks like it's only doing this when idle. As soon as I rescan, or reopen the program, it will start again at 0.0.0.0. Of course it never finishes all the way.
I'm curious to know what the idea behind this is - is it just trying to discover IP ranges with live devices?