Azure Active Directory Hybrid Health AD FS New Server

calendar Oct 12, 2023 · attack.defense_evasion attack.t1578  ·
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This detection uses azureactivity logs (Administrative category) to identify the creation or update of a server instance in an Azure AD Hybrid health AD FS service. A threat actor can create a new AD Health ADFS service and create a fake server instance to spoof AD FS signing logs. There is no need to compromise an on-prem AD FS server. This can be done programmatically via HTTP requests to Azure.

Sigma rule (View on GitHub)

 1title: Azure Active Directory Hybrid Health AD FS New Server
 2id: 288a39fc-4914-4831-9ada-270e9dc12cb4
 3status: test
 4description: |
 5    This detection uses azureactivity logs (Administrative category) to identify the creation or update of a server instance in an Azure AD Hybrid health AD FS service.
 6    A threat actor can create a new AD Health ADFS service and create a fake server instance to spoof AD FS signing logs. There is no need to compromise an on-prem AD FS server.
 7    This can be done programmatically via HTTP requests to Azure.    
 8references:
 9    - https://o365blog.com/post/hybridhealthagent/
10author: Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research), MSTIC
11date: 2021/08/26
12modified: 2023/10/11
13tags:
14    - attack.defense_evasion
15    - attack.t1578
16logsource:
17    product: azure
18    service: activitylogs
19detection:
20    selection:
21        CategoryValue: 'Administrative'
22        ResourceProviderValue: 'Microsoft.ADHybridHealthService'
23        ResourceId|contains: 'AdFederationService'
24        OperationNameValue: 'Microsoft.ADHybridHealthService/services/servicemembers/action'
25    condition: selection
26falsepositives:
27    - Legitimate AD FS servers added to an AAD Health AD FS service instance
28level: medium

References

  • Spoofing Azure AD sign-ins logs by imitating AD FS Hybrid Health Agent

    Azure AD Connect Health is a feature that allows viewing the health of on-prem hybrid infrastructure components, including Azure AD Connect and AD FS servers. Health information is gathered by agents installed on each on-prem hybrid server. Since March 2021, also AD FS sign-in events are gathered and sent to Azure AD. In this write-up (based on a Threat Analysis report by Secureworks), I’ll explain how anyone with a local administrator access to AD FS server (or proxy), can create arbitrary sign-ins events to Azure AD sign-ins log. Moreover, I’ll show how Global Administrators can register fake agents to Azure AD - even for tenants not using AD FS at all.


    Read More

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