There is only one forum when you install. It has these permissions:
schema_data wrote:# guests having read only access
# registered and registered_coppa having standard access
# global moderators having standard access + polls
# administrators having full forum and full moderator access
# Bots having bot access
By default, new forums are created with no permissions.
You can set them to that default by going into Forum Permissions, and removing the permissions from each forum.
No, all you have to do is go to the permissions page and remove all permissions, and all permissions will be reset to their default (original) settings as when the board was first installed...it's as simple as that.