I just banned them via core. After some time another batch connected, banned them as well. Seems to shut it down. I wonder how many other nodes are affected by this.
I haven't done that just yet. I'm trying to gather more information, but their constant disconnects are not helpful. If you take a closer look you will see that the amount of bandwidth that they spend is similar for all nodes and <1 MB. Additionally, the disconnect-reconnect interval seems to be
4559 minutes exact
(although I'll have to verify this).
Update: They disconnect every after some of them reach ~59 minutes connection time and they all disconnect at the same time (number of connections dropped from 86 to 45 in 1 second) after which they imminently start reconnecting.