GTRADE-003: Open-Join / External-Member Groups
- Platform
- Google Workspace
- Category
- Adversary Tradecraft
- Severity
- Medium
- Zero Trust pillar
- Visibility & Analytics (weight 1)
- Golden fixtures
- 3
- Branch coverage
- Observed: fixtures prove the verdicts they exercise
- Provenance
- baseline
What it checks
Groups that anyone (or anyone in the domain) can join, or that allow external members, widen the trust boundary and enable self-service access — if such a group also holds resource or IAM access, joining it inherits that access (a privilege-escalation path Google classifies as intended behavior).
Recommended value
Groups restricted to invited members; no anyone-can-join and no external members unless explicitly required
Remediation
Apps > Google Workspace > Groups for Business: set default 'Who can join' to 'Only invited users' and disable 'Allow external members' unless a group explicitly requires them; review groups that grant resource/IAM access.
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 | WARN |
| throttled | Not Assessed |
Framework mappings
- NIST SP 800-53
- AC-3, AC-6
- CIS Benchmark
- 1.x
- MITRE ATT&CK
- T1078, T1136