Hi ! How i can stop this ? Any help ? EDIT by Moderator: merged posts, please use the edit button instead of double posting.
What plugin are you using to prevent normal spam? I could try and ask the dev to implement a fix for this. Edit: It seems like it is more advanced than I thought... my idea wouldn't work...
http://forums.bukkit.org/threads/ch...-intelligent-anti-spam-system-1597-1-1.32890/ http://dev.bukkit.org/server-mods/mcbl/
If that doesn't work, there's nothing really that I can do. The attackers are using a VERY sophisticated program. Can you confirm in your server logs that they are all connecting with different IP addresses?