Xbox Live has no "Underground," "Anonymous," or "Hidden" mode. Your Gamertag, presence, and activity are visible per your privacy settings. Here's how to control visibility:
| Setting | Options | Effect |
|---|---|---|
| Others can see my profile | Everyone / Friends / Block | Hides bio, gamerscore, recent games |
| Others can see my real name | Friends / Block | Real name field (if set) |
| Others can communicate with me | Everyone / Friends / Block | Messages, party invites, voice |
| Others can see my activity feed | Everyone / Friends / Block | Hides "X started playing Y" |
| Share my presence | On / Off | Off = Appear Offline (still online, joinable by invite) |
| Game/Content sharing | On / Off | Home console sharing |
Summary: No "underground". Use Appear Offline + Privacy Settings + Private Party for maximum control.