Suspicious linking of existing user to external User
| Id | 22a320c2-e1e5-4c74-a35b-39fc9cdcf859 |
| Rulename | Suspicious linking of existing user to external User |
| Description | This query will detect when an attempt is made to update an existing user and link it to an guest or external identity. These activities are unusual and such linking of external identities should be investigated. In some cases you may see internal Entra ID sync accounts (Sync_) do this which may be benign |
| Severity | Medium |
| Tactics | PrivilegeEscalation |
| Techniques | T1078.004 |
| Required data connectors | AzureActiveDirectory |
| Kind | Scheduled |
| Query frequency | 1d |
| Query period | 1d |
| Trigger threshold | 0 |
| Trigger operator | gt |
| Source Uri | https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/SuspiciousLinkingofExternalIdtoExistingUsers.yaml |
| Version | 1.1.0 |
| Arm template | 22a320c2-e1e5-4c74-a35b-39fc9cdcf859.json |
AuditLogs
| where OperationName=~ "Update user"
| where Result =~ "success"
| mv-expand TargetResources
| mv-expand TargetResources.modifiedProperties
| extend displayName = tostring(TargetResources_modifiedProperties.displayName),
TargetUPN_oldValue = tostring(parse_json(tostring(TargetResources_modifiedProperties.oldValue))[0]),
TargetUPN_newValue = tostring(parse_json(tostring(TargetResources_modifiedProperties.newValue))[0])
| where displayName == "UserPrincipalName" and TargetUPN_oldValue !has "#EXT" and TargetUPN_newValue has "#EXT"
| extend InitiatingAppName = tostring(InitiatedBy.app.displayName)
| extend InitiatingAppServicePrincipalId = tostring(InitiatedBy.app.servicePrincipalId)
| extend InitiatingUserPrincipalName = tostring(InitiatedBy.user.userPrincipalName)
| extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
| extend InitiatingIPAddress = tostring(InitiatedBy.user.ipAddress)
| extend InitiatedBy = tostring(iff(isnotempty(InitiatingUserPrincipalName),InitiatingUserPrincipalName, InitiatingAppName))
| summarize arg_max(TimeGenerated, *) by CorrelationId
| project-reorder TimeGenerated, InitiatedBy, InitiatingAppName, InitiatingAppServicePrincipalId, InitiatingUserPrincipalName, InitiatingAadUserId, InitiatingIPAddress, TargetUPN_oldValue, TargetUPN_newValue
| extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])
| extend TargetAccountName = tostring(split(TargetUPN_oldValue, "@")[0]), TargetUPNSuffix = tostring(split(TargetUPN_oldValue, "@")[1])
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/SuspiciousLinkingofExternalIdtoExistingUsers.yaml
severity: Medium
query: |
AuditLogs
| where OperationName=~ "Update user"
| where Result =~ "success"
| mv-expand TargetResources
| mv-expand TargetResources.modifiedProperties
| extend displayName = tostring(TargetResources_modifiedProperties.displayName),
TargetUPN_oldValue = tostring(parse_json(tostring(TargetResources_modifiedProperties.oldValue))[0]),
TargetUPN_newValue = tostring(parse_json(tostring(TargetResources_modifiedProperties.newValue))[0])
| where displayName == "UserPrincipalName" and TargetUPN_oldValue !has "#EXT" and TargetUPN_newValue has "#EXT"
| extend InitiatingAppName = tostring(InitiatedBy.app.displayName)
| extend InitiatingAppServicePrincipalId = tostring(InitiatedBy.app.servicePrincipalId)
| extend InitiatingUserPrincipalName = tostring(InitiatedBy.user.userPrincipalName)
| extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
| extend InitiatingIPAddress = tostring(InitiatedBy.user.ipAddress)
| extend InitiatedBy = tostring(iff(isnotempty(InitiatingUserPrincipalName),InitiatingUserPrincipalName, InitiatingAppName))
| summarize arg_max(TimeGenerated, *) by CorrelationId
| project-reorder TimeGenerated, InitiatedBy, InitiatingAppName, InitiatingAppServicePrincipalId, InitiatingUserPrincipalName, InitiatingAadUserId, InitiatingIPAddress, TargetUPN_oldValue, TargetUPN_newValue
| extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])
| extend TargetAccountName = tostring(split(TargetUPN_oldValue, "@")[0]), TargetUPNSuffix = tostring(split(TargetUPN_oldValue, "@")[1])
description: |
' This query will detect when an attempt is made to update an existing user and link it to an guest or external identity. These activities are unusual and such linking of external
identities should be investigated. In some cases you may see internal Entra ID sync accounts (Sync_) do this which may be benign'
relevantTechniques:
- T1078.004
tactics:
- PrivilegeEscalation
requiredDataConnectors:
- connectorId: AzureActiveDirectory
dataTypes:
- AuditLogs
metadata:
author:
name: Microsoft Security Research
source:
kind: Community
categories:
domains:
- Security - Others
- Identity
support:
tier: Community
queryPeriod: 1d
entityMappings:
- entityType: Account
fieldMappings:
- identifier: Name
columnName: InitiatingAppName
- identifier: AadUserId
columnName: InitiatingAppServicePrincipalId
- entityType: Account
fieldMappings:
- identifier: FullName
columnName: InitiatingUserPrincipalName
- identifier: Name
columnName: InitiatingAccountName
- identifier: UPNSuffix
columnName: InitiatingAccountUPNSuffix
- entityType: Account
fieldMappings:
- identifier: AadUserId
columnName: InitiatingAadUserId
- entityType: Account
fieldMappings:
- identifier: FullName
columnName: TargetUPN_oldValue
- identifier: Name
columnName: TargetAccountName
- identifier: UPNSuffix
columnName: TargetUPNSuffix
- entityType: IP
fieldMappings:
- identifier: Address
columnName: InitiatingIPAddress
id: 22a320c2-e1e5-4c74-a35b-39fc9cdcf859
triggerThreshold: 0
triggerOperator: gt
name: Suspicious linking of existing user to external User
version: 1.1.0
tags:
- GuestorExternalIdentities
queryFrequency: 1d
kind: Scheduled
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"workspace": {
"type": "String"
}
},
"resources": [
{
"apiVersion": "2024-01-01-preview",
"id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/22a320c2-e1e5-4c74-a35b-39fc9cdcf859')]",
"kind": "Scheduled",
"name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/22a320c2-e1e5-4c74-a35b-39fc9cdcf859')]",
"properties": {
"alertRuleTemplateName": "22a320c2-e1e5-4c74-a35b-39fc9cdcf859",
"customDetails": null,
"description": "' This query will detect when an attempt is made to update an existing user and link it to an guest or external identity. These activities are unusual and such linking of external \nidentities should be investigated. In some cases you may see internal Entra ID sync accounts (Sync_) do this which may be benign'\n",
"displayName": "Suspicious linking of existing user to external User",
"enabled": true,
"entityMappings": [
{
"entityType": "Account",
"fieldMappings": [
{
"columnName": "InitiatingAppName",
"identifier": "Name"
},
{
"columnName": "InitiatingAppServicePrincipalId",
"identifier": "AadUserId"
}
]
},
{
"entityType": "Account",
"fieldMappings": [
{
"columnName": "InitiatingUserPrincipalName",
"identifier": "FullName"
},
{
"columnName": "InitiatingAccountName",
"identifier": "Name"
},
{
"columnName": "InitiatingAccountUPNSuffix",
"identifier": "UPNSuffix"
}
]
},
{
"entityType": "Account",
"fieldMappings": [
{
"columnName": "InitiatingAadUserId",
"identifier": "AadUserId"
}
]
},
{
"entityType": "Account",
"fieldMappings": [
{
"columnName": "TargetUPN_oldValue",
"identifier": "FullName"
},
{
"columnName": "TargetAccountName",
"identifier": "Name"
},
{
"columnName": "TargetUPNSuffix",
"identifier": "UPNSuffix"
}
]
},
{
"entityType": "IP",
"fieldMappings": [
{
"columnName": "InitiatingIPAddress",
"identifier": "Address"
}
]
}
],
"OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/SuspiciousLinkingofExternalIdtoExistingUsers.yaml",
"query": "AuditLogs\n| where OperationName=~ \"Update user\" \n| where Result =~ \"success\" \n| mv-expand TargetResources \n| mv-expand TargetResources.modifiedProperties \n| extend displayName = tostring(TargetResources_modifiedProperties.displayName), \nTargetUPN_oldValue = tostring(parse_json(tostring(TargetResources_modifiedProperties.oldValue))[0]), \nTargetUPN_newValue = tostring(parse_json(tostring(TargetResources_modifiedProperties.newValue))[0])\n| where displayName == \"UserPrincipalName\" and TargetUPN_oldValue !has \"#EXT\" and TargetUPN_newValue has \"#EXT\"\n| extend InitiatingAppName = tostring(InitiatedBy.app.displayName)\n| extend InitiatingAppServicePrincipalId = tostring(InitiatedBy.app.servicePrincipalId)\n| extend InitiatingUserPrincipalName = tostring(InitiatedBy.user.userPrincipalName)\n| extend InitiatingAadUserId = tostring(InitiatedBy.user.id)\n| extend InitiatingIPAddress = tostring(InitiatedBy.user.ipAddress)\n| extend InitiatedBy = tostring(iff(isnotempty(InitiatingUserPrincipalName),InitiatingUserPrincipalName, InitiatingAppName))\n| summarize arg_max(TimeGenerated, *) by CorrelationId\n| project-reorder TimeGenerated, InitiatedBy, InitiatingAppName, InitiatingAppServicePrincipalId, InitiatingUserPrincipalName, InitiatingAadUserId, InitiatingIPAddress, TargetUPN_oldValue, TargetUPN_newValue\n| extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, \"@\")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, \"@\")[1])\n| extend TargetAccountName = tostring(split(TargetUPN_oldValue, \"@\")[0]), TargetUPNSuffix = tostring(split(TargetUPN_oldValue, \"@\")[1])\n",
"queryFrequency": "P1D",
"queryPeriod": "P1D",
"severity": "Medium",
"subTechniques": [
"T1078.004"
],
"suppressionDuration": "PT1H",
"suppressionEnabled": false,
"tactics": [
"PrivilegeEscalation"
],
"tags": [
"GuestorExternalIdentities"
],
"techniques": [
"T1078"
],
"templateVersion": "1.1.0",
"triggerOperator": "GreaterThan",
"triggerThreshold": 0
},
"type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
}
]
}