I've known some gold farmers in my server. They do have a character that they play with, and the rest are all gold farming characters. They share with me their experience on how Joymax mass banned botter.
Here are some criteria on how they ban:
#1: ID that have near similar characters, just only a difference. For example, sky1, sky2, sky3, sky4 and so on.
If Joymax banned sky3 for botting, sky1, sky2, and sky4 will also be banned. This is mainly because gold farmers create such ID so that they can remember it easily as they can have up to 100 characters in a server.
#2: More than 5 ~ 9 similar account ID. For instance, bbs1, bbs2, bbs3, bbs4, bbs5. All these will get banned if one of them is caught botting. Meanwhile, if their ID are bbsa, bbsb, bbsc, which only 3 ID with the same characters, they are unlikely to face "all" ban if one of them get caught.
#3: Those IDs that are near similar having a character in 1 server. For example, they have IDs like 1egg, 2egg in Sparta, and 3egg, 4egg in another servers. If 1 of those IDs get caught, they are also unlikely to be caught.
Finally, I proved no accuracy that this is the way how Joymax ban. I'm just sharing with you my experience from my gold farming friends.
^_^
