"Teleporting" all over the map isn't just for hackers these days -- an issue with the way Blizzard synchronizes data between the servers and the clients allows anyone to mysteriously jump from place to place without the use of any third party software. I'm sure we've all been in groups where we see someone start to run forward and then continue running forward, right through a pack of mobs and into another and another... there's a moment of panic before you realize that, oh, they've just gotten disconnected, and none of those mobs noticed him at all.
What's happening is that Blizzard's servers know the person is disconnected (they're no longer synchronized with the server) and hasn't actually moved -- but on everyone else's screens, the character continues to do exactly what it had been doing previously. The purpose here is to keep the game running as smoothly as possible in a world of imperfect network connections. When someone experiences a lag spike and is de-synched from the server, Blizzard made the decision that they wanted game performance to look smooth to the rest of the players in the area -- so instead of freezing the de-synched player in place, the de-synched player continues doing just what they were doing before (at least on other player's screens). When the player re-synchs with the servers (he's no longer lagging, or he reconnects after a disconnect), Blizzard takes the client's data as the most accurate interpretation of events -- meaning that even while lagged, you can continue to play and issue commands as usual. (In this sort of system, you may not even notice lag unless it's quite extreme.) When you re-synch with the servers, Blizzard accepts what you were doing and synchronizes the game world to that. And for the most part this is entirely invisible to players, except for those few times when a lag spike turns into a longer disconnect.
The problem here is that players can recreate this issue manually. And while this little trick doesn't fool the servers (that know exactly where your player was when you de-synched from the server), it easily fools other players. So let's say you're in a PvP battleground, standing right next to another player -- you start running away and then de-synch yourself from the server. The other player sees you running away but in fact you're right next to them, and issuing commands that cause him grevious harm. The other player just sees what you were doing when you de-synched from the server, but when you re-synch, Blizzard will accept whatever commands you've been issuing as what really happened. End result? The other player sees you running away, and a few moments later is hit, instantaniously, with everything you've got to throw at him -- and is probably dead without any idea of what hit him.
What does Blizzard have to say about this -- obvious -- cheat? Well, when the folks over at Not Addicted found out about this problem, they decided to bring it to Blizzard's attention on the official forums -- only to be derided by posters explaining that this has been a known issue in the game since the introduction of Warsong Gulch, but it hasn't been changed it yet. So is this another issue of "creative use of game mechanics," perhaps? For now, at least, Blizzard is keeping quiet. And if they haven't done anything about it now, I can't say it's likely that they're going to any time soon.
For those interested in more of the technical details on this, PlayNoEvil has a great run-down.
[Fan art by Guillaume Bonnet]