The cause was not an external attack but a huge amount of primed TNT on the affected game server, which overloaded the port. We removed the TNT; the server runs normally again and is reachable for all players. This incident is resolved.

The blocked port has been open again since 13:53 UTC, and the server is reachable for all players again. The source of the attacks stays blocked. We will keep monitoring for a while.

We found the source: both attacks today (05:04 and 13:44 UTC) came almost entirely from the same address. It is now permanently blocked on Node 3. The affected port stays closed for now until we are sure no further attacks follow.

Node 3 has been under attack again since 13:44 UTC. Our protection automatically blocked the attacked port of one game server to keep the rest of the node stable. Java players currently cannot reach this one server; all other servers on Node 3 run normally. We are looking into the attack and will unblock the port as soon as it is safe.