User Account Created Using Incorrect Naming Format | Microsoft Sentinel Analytic Rules

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Id	ee55dc85-d2da-48c1-a6c0-3eaee62a8d56
Rulename	User Account Created Using Incorrect Naming Format
Description	This query looks for accounts being created where the name does not match a defined pattern. Attackers may attempt to add accounts as a means of establishing persistant access to an environment, looking for anomalies in created accounts may help identify illegitimately created accounts. Created accounts should be investigated to ensure they were legitimated created. The user_regex field in the query needs to be populated with the expected pattern for the environment before deployment. Ref: https://docs.microsoft.com/azure/active-directory/fundamentals/security-operations-user-accounts#accounts-not-following-naming-policies
Severity	Low
Tactics	Persistence
Techniques	T1136.003
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/UserAccountCreatedUsingIncorrectNamingFormat.yaml
Version	1.1.0
Arm template	ee55dc85-d2da-48c1-a6c0-3eaee62a8d56.json

KQL

// Add the environments expected username format regex below before deploying
let user_regex = "";
AuditLogs
| where OperationName =~ "Add user"
| where Result =~ "success"
| extend userAgent = tostring(AdditionalDetails[0].value)
| 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))
| extend AddedUser = tostring(TargetResources[0].userPrincipalName)
| where AddedUser matches regex user_regex
| extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])
| extend TargetAccountName = tostring(split(AddedUser, "@")[0]), TargetAccountUPNSuffix = tostring(split(AddedUser, "@")[1])

YAML

triggerOperator: gt
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/UserAccountCreatedUsingIncorrectNamingFormat.yaml
description: |
  'This query looks for accounts being created where the name does not match a defined pattern.
    Attackers may attempt to add accounts as a means of establishing persistant access to an environment, looking for anomalies in created accounts may help identify illegitimately created accounts.
    Created accounts should be investigated to ensure they were legitimated created.
    The user_regex field in the query needs to be populated with the expected pattern for the environment before deployment.
    Ref: https://docs.microsoft.com/azure/active-directory/fundamentals/security-operations-user-accounts#accounts-not-following-naming-policies'
triggerThreshold: 0
relevantTechniques:
- T1136.003
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: AddedUser
  - identifier: Name
    columnName: TargetAccountName
  - identifier: UPNSuffix
    columnName: TargetAccountUPNSuffix
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: InitiatingIPAddress
tags:
- AADSecOpsGuide
version: 1.1.0
query: |
  // Add the environments expected username format regex below before deploying
  let user_regex = "";
  AuditLogs
  | where OperationName =~ "Add user"
  | where Result =~ "success"
  | extend userAgent = tostring(AdditionalDetails[0].value)
  | 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))
  | extend AddedUser = tostring(TargetResources[0].userPrincipalName)
  | where AddedUser matches regex user_regex
  | extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])
  | extend TargetAccountName = tostring(split(AddedUser, "@")[0]), TargetAccountUPNSuffix = tostring(split(AddedUser, "@")[1])
queryPeriod: 1d
name: User Account Created Using Incorrect Naming Format
kind: Scheduled
id: ee55dc85-d2da-48c1-a6c0-3eaee62a8d56
tactics:
- Persistence
severity: Low
metadata:
  source:
    kind: Community
  support:
    tier: Community
  author:
    name: Microsoft Security Research
  categories:
    domains:
    - Security - Others
requiredDataConnectors:
- dataTypes:
  - AuditLogs
  connectorId: AzureActiveDirectory
queryFrequency: 1d

ARM

{
  "$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/ee55dc85-d2da-48c1-a6c0-3eaee62a8d56')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/ee55dc85-d2da-48c1-a6c0-3eaee62a8d56')]",
      "properties": {
        "alertRuleTemplateName": "ee55dc85-d2da-48c1-a6c0-3eaee62a8d56",
        "customDetails": null,
        "description": "'This query looks for accounts being created where the name does not match a defined pattern.\n  Attackers may attempt to add accounts as a means of establishing persistant access to an environment, looking for anomalies in created accounts may help identify illegitimately created accounts.\n  Created accounts should be investigated to ensure they were legitimated created.\n  The user_regex field in the query needs to be populated with the expected pattern for the environment before deployment.\n  Ref: https://docs.microsoft.com/azure/active-directory/fundamentals/security-operations-user-accounts#accounts-not-following-naming-policies'\n",
        "displayName": "User Account Created Using Incorrect Naming Format",
        "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": "AddedUser",
                "identifier": "FullName"
              },
              {
                "columnName": "TargetAccountName",
                "identifier": "Name"
              },
              {
                "columnName": "TargetAccountUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "InitiatingIPAddress",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/UserAccountCreatedUsingIncorrectNamingFormat.yaml",
        "query": "// Add the environments expected username format regex below before deploying\nlet user_regex = \"\";\nAuditLogs\n| where OperationName =~ \"Add user\"\n| where Result =~ \"success\"\n| extend userAgent = tostring(AdditionalDetails[0].value)\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| extend AddedUser = tostring(TargetResources[0].userPrincipalName)\n| where AddedUser matches regex user_regex\n| extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, \"@\")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, \"@\")[1])\n| extend TargetAccountName = tostring(split(AddedUser, \"@\")[0]), TargetAccountUPNSuffix = tostring(split(AddedUser, \"@\")[1])\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Low",
        "subTechniques": [
          "T1136.003"
        ],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Persistence"
        ],
        "tags": [
          "AADSecOpsGuide"
        ],
        "techniques": [
          "T1136"
        ],
        "templateVersion": "1.1.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}