Attendees automatically become visible when they first register. The default for new users can be changed in your Settings> People and Profiles> Defaults settings. However, you can also make individual attendees invisible in the front-facing app, so that they can use the app but not appear in the Attendee listings.
- Select People
- Locate and click on the profile you'd like to change
- Select the Preferences tab
- Click checkbox for "Hide this profile from other attendees" and Save.