User Account Created Using Incorrect Naming Format

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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

tags:
- AADSecOpsGuide
id: ee55dc85-d2da-48c1-a6c0-3eaee62a8d56
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
entityMappings:
- 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: Account
- fieldMappings:
  - columnName: InitiatingIPAddress
    identifier: Address
  entityType: IP
version: 1.1.0
triggerOperator: gt
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])  
tactics:
- Persistence
kind: Scheduled
queryFrequency: 1d
name: User Account Created Using Incorrect Naming Format
severity: Low
metadata:
  author:
    name: Microsoft Security Research
  source:
    kind: Community
  categories:
    domains:
    - Security - Others
  support:
    tier: Community
queryPeriod: 1d
requiredDataConnectors:
- dataTypes:
  - AuditLogs
  connectorId: AzureActiveDirectory
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/AuditLogs/UserAccountCreatedUsingIncorrectNamingFormat.yaml
relevantTechniques:
- T1136.003

ARM