Is there a way to limit visibility to a confidential project, perhaps only to the project owner and project team?

Hi Pamela - go into the project sharing and remove Inherited Permissions from the project, it should only be the owner, project team, and of course system admins.

One thing, also check the People/Staffing area (not sure which interface you are using) and remove any access people as well.

Under Project actions, you have the ability to limit sharing of the project to specific teams and/or individuals. Hope that helps.