Community Tracker has a very rich set of permissions built in. You can decide which users can view or edit which topics.
The permission system is group based, out-of-the-box the system defines 3 groups: (everyone, developer and admins) you can add any groups you wish and add users to each group.
Additionally you can change the global settings on the tracker to disable public access if you wish to only provide support to, say, paying customers.