Multiboxing in World of Warcraft is as old as the game itself but Blizzard are finally putting a stop to it and it appears that the players are happy about the change.
Multiboxing is the practice of a single-player running several characters at the same time. This is done through having more than one account and while it could be done through controlling more than one PC, it has been mostly done by running multiple copies of World of Warcraft on a single machine in the past years.
As a result, the player can do activities that would ordinarily require a team but the big problem WoW population has with multiboxers is their ability to farm up resources with the multiplier equal to the number of characters they are running. The big catch here is that the player just uses one character to input the commands and software mirrors those inputs to other clients.
This is the part Blizzard will prevent in the future. The official announcement of the policy change noted that third-party input broadcasting software will become illegal in World of Warcraft. Furthermore, the post says that besides multiboxing, it also fortifies the use of bots, which is something no game really wants, with the rare exception of players liking them for holding up the economy in games that are on maintenance mode.
Anyway, Blizzard has had it with input broadcasts and will issue warnings to players who are detected to be using such software. If they persist despite the warnings, Blizz will "escalate to account actions" which will include suspensions and even permanent bans .