Blizzard Entertainment banned "several thousands "of Diablo III battle.net accounts for using third-party programs within the game, according to a statement on the company's official forums.
Here is the official statement from Blizzard Entertainment's forum:
"We've recently issued account bans to several thousand Diablo III players who were found to be using botting programs while playing. In addition to undermining the spirit of fair play, botting, hacking, and other forms of cheating can also cause technical problems with the game as well as contribute to performance issues with the Battle.net service. To learn more about our exploitation policy for Diablo III and how it may affect your gameplay, please visit our official support site.
As always, maintaining a stable, safe, and enjoyable online environment for legitimate players is very important to us, and we'll be continuing to keep watch on Battle.net and take action as needed. In the meantime, if you wish to report the possible use of botting programs to Blizzard, please see this thread for more information. We will also be adding the ability for players to report this kind of behavior directly through the game client in a future patch."
In Blizzard's Technical Support Forum a moderator defined third-party software and other prohibited actions to a banned player.
Here are the ban worthy offenses from Blizzard's Technical Support Forum:
Unapproved Third Party Software
A third party program is any file or program that is used in addition to the game to gain an unfair advantage. These programs may increase movement speed or teleport heroes from one place to another beyond what is allowed by game design. It also includes any programs that obtain information from the game that is not normally available to the regular player or that transmit or modify any of the game files.
Cheat Programs ("Hacks")
We take action against accounts using hacks when a hero on the account is identified using a hack program. Hacks provide benefits normally not achievable in the game. Such benefits may include: increased speed, teleportation, or running through walls.
Automation Programs ("Bots")
We take action against accounts using automation programs or bots when one or more heroes on the account are identified using a bot to achieve automation.