This has been known since Open Beta, nothing new.
Game allows every random dude on internet to see complete unmasked IP of the players they are playing with. All they need is a software to terminate those connections. Especially if he is the host, everyone else gets an error, and he gets a free win vs bots.
Don't even get me on DDoS ing your opponent, because it is way worse.
Ah also there is lagswitchers.
As you see PROs of P2P heavily weight its CONs. *facepalm*