@Alice: Your blabla isn't answering his question!
@celux: There are Usergroup- and channel-permissions you could ristrict the channels to specific usergroups.
If you gave a usergroup the permission (/admincp/usergroup.php?do=modify&) to see the content and a user is part of that group he will have access. If not he can't see the channel.
Is that what you are lokking for?
http://vb5support.com/introduction
https://www.vbulletin.com/en/learn-more/