{
  "case_id": "CASE-2026-1001",
  "title": "Impossible travel login followed by MFA prompt fatigue",
  "scenario": "o365_suspicious_login",
  "alert_type": "azuread_impossible_travel",
  "severity": "high",
  "status": "confirmed",
  "time_window": {"start": "2026-04-02T22:10:00+08:00", "end": "2026-04-02T23:30:00+08:00"},
  "summary": "User account showed impossible travel between Shanghai and Amsterdam, followed by repeated MFA prompts and successful sign-in.",
  "alert_source": "Microsoft Entra ID",
  "entities": {"users": ["david@corp.example"], "hosts": ["WS-DAVID-01"], "mailboxes": ["david@corp.example"]},
  "observables": {"ips": ["203.0.113.150", "198.51.100.61"], "domains": [], "urls": [], "hashes": []},
  "evidence": ["Two successful sign-ins from geographically impossible locations within 15 minutes.", "MFA challenge volume increased abnormally before final success.", "User confirmed they did not initiate overseas login."],
  "investigation_steps": ["Review sign-in logs and device IDs.", "Check MFA event sequence.", "Validate user travel status with manager."],
  "conclusion": {"verdict": "true_positive", "reason": "Impossible travel plus user denial and MFA fatigue pattern.", "recommended_actions": ["Revoke sessions and reset credentials.", "Review mailbox rules and app consent."]},
  "related_refs": {"playbooks": ["PB-O365-LOGIN-001"], "kb": ["KB-O365-IMPOSSIBLE-TRAVEL", "KB-O365-MFA-FATIGUE"], "cases": []},
  "lessons_learned": ["Impossible travel needs to be combined with user confirmation and MFA telemetry."],
  "tags": ["o365", "login", "impossible-travel", "mfa-fatigue"]
}