I confirm Psihius's comments about the huge traffic spike hitting the trackers. This is our traffic graph for the last days: http://img717.imageshack.us/img717/9905/hwgraphphp.png This aggregates both the front-end/web interface trafic and the back-end/tracker trefic. Blue is incoming, green is outgoing. As you can see, we went from a regular, mostly upstream web host, to having the upstream comparable with the downstream because of the bogus requests. The incoming traffic trebled. The outgoing traffic increased moderately because it was high from the regular load (forums, torrent downloads etc.) and the reply from the tracker is very short: "HTTP/1.0 200 OK\r\n\r\nd14:failure reason20:unregistered torrente" I went ballistic when I saw this, thought we were attacked . A trafic dump showed allot of "unregistered torrent" queries, all coming from uTorrent 2.0.4 clients, and a Google search later here I am. Fortunately, our tracker is not PHP based, but a much more capable compiled daemon, that can still handle the load with a ~ 15% CPU usage.
