M365 Potential AiTM UserLoggedIn via Office App (Tycoon2FA)
Detects Microsoft 365 audit "UserLoggedIn" events consistent with Tycoon 2FA phishing-as-a-service (PhaaS) adversary-in-the-middle (AiTM) activity: the Microsoft Authentication Broker requesting access where the…
Description
Detects Microsoft 365 audit "UserLoggedIn" events consistent with Tycoon 2FA phishing-as-a-service (PhaaS) adversary-in-the-middle (AiTM) activity: the Microsoft Authentication Broker requesting access where the object identifier matches Microsoft Graph or Exchange Online, or the Office web client application authenticating to itself, combined with Node.js-style user agents (node, axios, undici). Tycoon 2FA bypasses MFA by relaying authentication and capturing session material, often targeting Microsoft 365 and Gmail. Baseline legitimate automation and developer tooling before tuning.
Detection logic
Its licence does not clear it for publishing here
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Detection requirements
- Platform
- Identity ProviderLinuxmacOSOffice SuiteSaaSWindows
The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.
- Log source category
- event_index
Known benign triggers
- Legitimate Node.js or undici-based automation, health checks, or internal services that use the Microsoft Authentication Broker or the same first-party application IDs against Graph or Exchange may match. Developers using axios or undici with delegated flows can also resemble this pattern.
MITRE ATT&CK mappings
0 exclusive techniques.This is coverage no other published rule has; it is not this rule's total technique count.
References
| Reference | Cited by |
|---|---|
| any.run/malware-trends/tycoon/ | 12 |
From the source
- At source
- Open at source
- Upstream identifier
- 275b972d-2fed-44fc-9214-08603b3318e3
- Tagged by the source as
- Data Source: Microsoft 365Data Source: Microsoft 365 Audit LogsDomain: CloudDomain: EmailDomain: IdentityDomain: SaaSNoise: UnknownPerformance: NormalPlatform: Microsoft 365Profile: RecommendedResources: Investigation GuideRule Type: Custom Query (KQL)Tactic: Credential AccessTactic: Initial AccessThreat: AiTM PhishingThreat: Tycoon2FAUse Case: Threat Detection
Licence
- Published under
- Elastic License 2.0Read the licence
- Attribution
- Required
Authorship
- Written by
- Published
- Sep 20, 2026
- Version
- 3