M365EXO-027: Attachment filter assesses true file type (MS.EXO.9.2)
- Plataforma
- Entra ID / M365
- Categoría
- Advanced Threat Protection
- Severidad
- Medium
- Pilar de Zero Trust
- Applications & Workloads (peso 1)
- Fixtures de referencia
- 3
- Cobertura de ramas
- Observada: los fixtures prueban los veredictos que ejercitan
- Procedencia
- baseline
Qué comprueba
SCuBA MS.EXO.9.2 recommends that the attachment filter attempt to determine the true file type and assess the file extension. Attackers rename files to disguise dangerous types (for example, renaming an executable to a .txt). True-type detection catches mismatches where the extension does not match the actual file content, closing a common evasion technique.
Valor recomendado
Attachment filtering configured to inspect true file type rather than relying on the file extension alone
Remediación
Ensure the attachment filtering solution inspects the actual file content to determine the true type rather than trusting the file extension. In the native solution this is provided by the common attachment filter's type detection; verify it is enabled. For third-party gateways, confirm true-type or content-based inspection is configured so renamed dangerous files are still caught.
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
- NIST SP 800-53
- SI-3
- MITRE ATT&CK
- T1036.008