Prevent certain servers from /server

Hi,
The way I currently have my bungeecoord servers set up is they join on the default server, the hub. From this hub they can teleport to the minigame hub. From this minigame hub, they can choose what minigame they go into. However I don't want them to be able to type /server tntrungame1 and avoid join signs. Is it possible to block certain servers from showing up on /server? Thanks