Users Authenticating To Other Azure AD Tenants — Sigma Rule

Rule metadata and linked tags

Author: MikeDuddington, '@dudders1'. Source status: test; severity: medium. Source dates: 2022-06-30 / not supplied.

{
  "product": "azure",
  "service": "signinlogs"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 04363118027bb65a71a325cc8523291daeeaedbbcdaa8879d3042bd037b00a6c

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Users Authenticating To Other Azure AD Tenants
id: 5f521e4b-0105-4b72-845b-2198a54487b9
status: test
description: Detect when users in your Azure AD tenant are authenticating to other Azure AD Tenants.
references:
    - https://learn.microsoft.com/en-gb/entra/architecture/security-operations-user-accounts#monitoring-external-user-sign-ins
author: MikeDuddington, '@dudders1'
date: 2022-06-30
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.initial-access
    - attack.stealth
    - attack.t1078.004
logsource:
    product: azure
    service: signinlogs
detection:
    selection:
        Status: 'Success'
        HomeTenantId: 'HomeTenantID'
    filter:
        ResourceTenantId|contains: 'HomeTenantID'
    condition: selection and not filter
falsepositives:
    - If this was approved by System Administrator.
level: medium

Original YAML and metadata in JSON

False positives

• If this was approved by System Administrator.

Source references

• https://learn.microsoft.com/en-gb/entra/architecture/security-operations-user-accounts#monitoring-external-user-sign-ins