[MC-823] Packets generated by third parties can cause heavy lag

Basically, certain poorly designed third party clients can cause heavy lag in multiplayer.
Minecraft 1.3.1 and prior did not handle this very well at all. Once a third party client did this, the server would go unresponsive and eventually crash. But in 1.4, the CPU goes into very high utilization and recovers, usually within two minutes.
During the recovery time, there is very heavy lag noticed by all the players still connected.
So a lot of progress has been made to improve the situation since 1.3.1. I'm sure it's not a trivial task to make it even better, but this lag is highly disruptive. Of course, adding a whitelist would mitigate it greatly, some servers opt to go without a whitelist.
Here is an example from the server log of the kind of activity that causes this situation.
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [INFO] KARLOX_11 lost connection: disconnect.endOfStream