Microsoft Entra ID Health Service Agents Registry Keys Access

Description

'This detection uses Windows security events to detect suspicious access attempts to the registry key values and sub-keys of Microsoft Entra ID Health service agents (e.g AD FS). Information from AD Health service agents can be used to potentially abuse some of the features provided by those services in the cloud (e.g. Federation). This detection requires an access control entry (ACE) on the system access control list (SACL) of the following securable object: HKLM:\SOFTWARE\Microsoft\ADHealthAgent. Make sure you set the SACL to propagate to its sub-keys. You can find more information in here https://github.com/OTRF/Set-AuditRule/blob/master/rules/registry/aad_connect_health_service_agent.yml '

Query · kql

// ADHealth Monitoring Agent Registry Key
let aadHealthMonAgentRegKey = "\\REGISTRY\\MACHINE\\SOFTWARE\\Microsoft\\MicrosoftOnline\\Reporting\\MonitoringAgent";
// Filter out known processes
let aadConnectHealthProcs = dynamic ([
    'Microsoft.Identity.Health.Adfs.DiagnosticsAgent.exe',
    'Microsoft.Identity.Health.Adfs.InsightsService.exe',
    'Microsoft.Identity.Health.Adfs.MonitoringAgent.Startup.exe',
    'Microsoft.Identity.Health.Adfs.PshSurrogate.exe',
    'Microsoft.Identity.Health.Common.Clients.ResourceMonitor.exe',
    'Microsoft.Identity.Health.AadSync.MonitoringAgent.Startup.exe',
    'Microsoft.Identity.AadConnect.Health.AadSync.Host.exe',
    'Microsoft.Azure.ActiveDirectory.Synchronization.Upgrader.exe',
    'miiserver.exe'
]);
(union isfuzzy=true
(
SecurityEvent
| where EventID == '4656'
| where EventData has aadHealthMonAgentRegKey
| extend EventData = parse_xml(EventData).EventData.Data
| mv-expand bagexpansion=array EventData
| evaluate bag_unpack(EventData)
| extend Key = tostring(column_ifexists('@Name', "")), Value = column_ifexists('#text', "")
| evaluate pivot(Key, any(Value), TimeGenerated, Computer, EventID)
| extend ObjectName = column_ifexists("ObjectName", ""),
    ObjectType = column_ifexists("ObjectType", "")
| where ObjectType == 'Key'
| where ObjectName == aadHealthMonAgentRegKey
| extend SubjectUserName = column_ifexists("SubjectUserName", ""),
    SubjectDomainName = column_ifexists("SubjectDomainName", ""),
    ProcessName = column_ifexists("ProcessName", "")
| extend Process = split(ProcessName, '\\', -1)[-1],
    Account = strcat(SubjectDomainName, "\\", SubjectUserName)
| where Process !in (aadConnectHealthProcs)
| summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
),
  ( WindowsEvent
| where EventID == '4656' and EventData has aadHealthMonAgentRegKey
| extend ObjectType = tostring(EventData.ObjectType)
| where ObjectType == 'Key'
| extend ObjectName = tostring(EventData.ObjectName)
| where ObjectName == aadHealthMonAgentRegKey
| extend ProcessName = tostring(EventData.ProcessName)
| extend Process = tostring(split(ProcessName, '\\')[-1])
| where Process !in (aadConnectHealthProcs)
| extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
| extend SubjectUserName = tostring(EventData.SubjectUserName)
| extend SubjectDomainName = tostring(EventData.SubjectDomainName)
| summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
),
(
SecurityEvent
| where EventID == '4663'
| where ObjectType == 'Key'
| where ObjectName == aadHealthMonAgentRegKey
| extend Process = tostring(split(ProcessName, '\\', -1)[-1])
| where Process !in (aadConnectHealthProcs)
| summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
),
( WindowsEvent
| where EventID == '4663' and EventData has aadHealthMonAgentRegKey
| extend ObjectType = tostring(EventData.ObjectType)
| where ObjectType == 'Key'
| extend ObjectName = tostring(EventData.ObjectName)
| where ObjectName == aadHealthMonAgentRegKey
| extend ProcessName = tostring(EventData.ProcessName)
| extend Process = tostring(split(ProcessName, '\\')[-1])
| where Process !in (aadConnectHealthProcs)
| extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
| extend SubjectUserName = tostring(EventData.SubjectUserName)
| extend SubjectDomainName = tostring(EventData.SubjectDomainName)
| summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
)
)
// You can filter out potential machine accounts
//| where AccountType != 'Machine'
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
| extend Name = tostring(split(Account, "\\")[1]), NTDomain = tostring(split(Account, "\\")[0])
Raw source Microsoft Entra ID Health Service Agents Registry Keys Access · KQL
Esc
Published by Azure/Azure-Sentinel ↗, licensed under MIT ↗. Reproduced here unmodified. 
id: 06bbf969-fcbe-43fa-bac2-b2fa131d113a
name: Microsoft Entra ID Health Service Agents Registry Keys Access
description: |
  'This detection uses Windows security events to detect suspicious access attempts to the registry key values and sub-keys of Microsoft Entra ID Health service agents (e.g AD FS).
  Information from AD Health service agents can be used to potentially abuse some of the features provided by those services in the cloud (e.g. Federation).
  This detection requires an access control entry (ACE) on the system access control list (SACL) of the following securable object: HKLM:\SOFTWARE\Microsoft\ADHealthAgent.
  Make sure you set the SACL to propagate to its sub-keys. You can find more information in here https://github.com/OTRF/Set-AuditRule/blob/master/rules/registry/aad_connect_health_service_agent.yml
  '
severity: Medium
requiredDataConnectors:
  - connectorId: SecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: WindowsSecurityEvents
    dataTypes: 
      - SecurityEvents 
  - connectorId: WindowsForwardedEvents
    dataTypes: 
      - WindowsEvent 
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Collection
relevantTechniques:
  - T1005
tags:
  - SimuLand
query: |
  // ADHealth Monitoring Agent Registry Key
  let aadHealthMonAgentRegKey = "\\REGISTRY\\MACHINE\\SOFTWARE\\Microsoft\\MicrosoftOnline\\Reporting\\MonitoringAgent";
  // Filter out known processes
  let aadConnectHealthProcs = dynamic ([
      'Microsoft.Identity.Health.Adfs.DiagnosticsAgent.exe',
      'Microsoft.Identity.Health.Adfs.InsightsService.exe',
      'Microsoft.Identity.Health.Adfs.MonitoringAgent.Startup.exe',
      'Microsoft.Identity.Health.Adfs.PshSurrogate.exe',
      'Microsoft.Identity.Health.Common.Clients.ResourceMonitor.exe',
      'Microsoft.Identity.Health.AadSync.MonitoringAgent.Startup.exe',
      'Microsoft.Identity.AadConnect.Health.AadSync.Host.exe',
      'Microsoft.Azure.ActiveDirectory.Synchronization.Upgrader.exe',
      'miiserver.exe'
  ]);
  (union isfuzzy=true
  (
  SecurityEvent
  | where EventID == '4656'
  | where EventData has aadHealthMonAgentRegKey
  | extend EventData = parse_xml(EventData).EventData.Data
  | mv-expand bagexpansion=array EventData
  | evaluate bag_unpack(EventData)
  | extend Key = tostring(column_ifexists('@Name', "")), Value = column_ifexists('#text', "")
  | evaluate pivot(Key, any(Value), TimeGenerated, Computer, EventID)
  | extend ObjectName = column_ifexists("ObjectName", ""),
      ObjectType = column_ifexists("ObjectType", "")
  | where ObjectType == 'Key'
  | where ObjectName == aadHealthMonAgentRegKey
  | extend SubjectUserName = column_ifexists("SubjectUserName", ""),
      SubjectDomainName = column_ifexists("SubjectDomainName", ""),
      ProcessName = column_ifexists("ProcessName", "")
  | extend Process = split(ProcessName, '\\', -1)[-1],
      Account = strcat(SubjectDomainName, "\\", SubjectUserName)
  | where Process !in (aadConnectHealthProcs)
  | summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
  ),
    ( WindowsEvent
  | where EventID == '4656' and EventData has aadHealthMonAgentRegKey
  | extend ObjectType = tostring(EventData.ObjectType)
  | where ObjectType == 'Key'
  | extend ObjectName = tostring(EventData.ObjectName)
  | where ObjectName == aadHealthMonAgentRegKey
  | extend ProcessName = tostring(EventData.ProcessName)
  | extend Process = tostring(split(ProcessName, '\\')[-1])
  | where Process !in (aadConnectHealthProcs)
  | extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
  | extend SubjectUserName = tostring(EventData.SubjectUserName)
  | extend SubjectDomainName = tostring(EventData.SubjectDomainName)
  | summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
  ),
  (
  SecurityEvent
  | where EventID == '4663'
  | where ObjectType == 'Key'
  | where ObjectName == aadHealthMonAgentRegKey
  | extend Process = tostring(split(ProcessName, '\\', -1)[-1])
  | where Process !in (aadConnectHealthProcs)
  | summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
  ),
  ( WindowsEvent
  | where EventID == '4663' and EventData has aadHealthMonAgentRegKey
  | extend ObjectType = tostring(EventData.ObjectType)
  | where ObjectType == 'Key'
  | extend ObjectName = tostring(EventData.ObjectName)
  | where ObjectName == aadHealthMonAgentRegKey
  | extend ProcessName = tostring(EventData.ProcessName)
  | extend Process = tostring(split(ProcessName, '\\')[-1])
  | where Process !in (aadConnectHealthProcs)
  | extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
  | extend SubjectUserName = tostring(EventData.SubjectUserName)
  | extend SubjectDomainName = tostring(EventData.SubjectDomainName)
  | summarize StartTime = max(TimeGenerated), EndTime = min(TimeGenerated), count() by EventID, Account, Computer, Process, SubjectUserName, SubjectDomainName, ObjectName, ObjectType, ProcessName
  )
  )
  // You can filter out potential machine accounts
  //| where AccountType != 'Machine'
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
  | extend Name = tostring(split(Account, "\\")[1]), NTDomain = tostring(split(Account, "\\")[0])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: Account
      - identifier: Name
        columnName: Name
      - identifier: NTDomain
        columnName: NTDomain
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: HostNameDomain
version: 1.1.5
kind: Scheduled
metadata:
    source:
        kind: Community
    author:
        name: Microsoft Security Research
    support:
        tier: Community
    categories:
        domains: [ "Security - Others", "Identity" ]

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