M365EXO-021: Contact folder sharing not open to all domains (MS.EXO.6.1)
- Plataforma
- Entra ID / M365
- Categoría
- Advanced Threat Protection
- Severidad
- Medium
- Pilar de Zero Trust
- Data (peso 1)
- Fixtures de referencia
- 3
- Cobertura de ramas
- Observada: los fixtures prueban los veredictos que ejercitan
- Procedencia
- baseline
Qué comprueba
SCuBA MS.EXO.6.1 requires that contact folders not be shared with all domains. Exchange Online sharing policies can relax the default restriction on outbound contact sharing. A policy that shares contacts with all domains (a '*' domain entry) exposes directory and contact data broadly, creating a data exfiltration avenue and aiding reconnaissance for social engineering.
Valor recomendado
No sharing policy rule grants contact sharing to the wildcard domain (*); sharing limited to specific approved domains only
Remediación
Review every Exchange Online sharing policy and remove any rule that shares contact folders with the wildcard domain (*). Where external contact sharing is genuinely required, scope it to specific named partner domains rather than all domains. Validate that the default sharing policy does not silently re-enable all-domain contact sharing.
Veredictos probados con fixtures
Cada veredicto de esta tabla está probado por un fixture de referencia en la suite de pruebas que valida el módulo. La tabla se deriva de la última ejecución en verde; no puede editarse a mano.
| Escenario | Veredicto esperado |
|---|---|
| clean | PASS |
| known-bad | FAIL |
| throttled | Not Assessed |
Mapeos a marcos de referencia
- CISA SCuBA
- MS.EXO.6.1v1
- NIST SP 800-53
- AC-4, AC-21
- MITRE ATT&CK
- T1087