M365TEAMS-004: Anonymous meeting join settings
- Platform
- Entra ID / M365
- Category
- Microsoft Teams Security
- Severity
- High
- Zero Trust pillar
- Applications & Workloads (weight 2)
- Golden fixtures
- 3
- Branch coverage
- Observed: fixtures prove the verdicts they exercise
- Provenance
- baseline
What it checks
Anonymous meeting join allows anyone with a meeting link to join Teams meetings without authentication, making it impossible to verify the identity of participants. This setting is frequently exploited in meeting bombing attacks where uninvited participants join to disrupt meetings or eavesdrop on confidential discussions. Disabling anonymous join or requiring all participants to authenticate significantly improves meeting security.
Recommended value
Anonymous meeting join disabled; all meeting participants required to authenticate; lobby enabled for unauthenticated users
Remediation
Disable anonymous meeting join in the Teams meeting policy to require all participants to sign in before joining meetings. If anonymous join must be allowed for specific use cases such as public webinars, create a separate meeting policy with anonymous join enabled and assign it only to the users who need it. Enable the lobby for all external and guest participants and configure meeting organizers to manually admit attendees from the lobby.
Fixture-proven verdicts
Every verdict below is proven by a golden fixture in the module's gating test suite. This table derives from the last green run; it cannot be edited by hand.
| Scenario | Expected verdict |
|---|---|
| clean | PASS |
| known-bad | FAIL |
| throttled | Not Assessed |
Framework mappings
- CISA SCuBA
- MS.TEAMS.1.2v2, MS.TEAMS.1.3v1
- NIST SP 800-53
- AC-14
- CIS M365 Benchmark
- 8.5.2