Suspicious Login from deleted guest account

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Id	defe4855-0d33-4362-9557-009237623976
Rulename	Suspicious Login from deleted guest account
Description	This query will detect logins from guest account which was recently deleted. For any successful logins from deleted identities should be investigated further if any existing user accounts have been altered or linked to such identity prior deletion
Severity	Medium
Tactics	PrivilegeEscalation
Techniques	T1078.004
Required data connectors	AzureActiveDirectory
Kind	Scheduled
Query frequency	1h
Query period	1d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/MultipleDataSources/SuspiciousLoginfromDeletedExternalIdentities.yaml
Version	1.0.5
Arm template	defe4855-0d33-4362-9557-009237623976.json

KQL

let query_frequency = 1h;
let query_period = 1d;
AuditLogs
| where TimeGenerated > ago(query_frequency)
| where Category =~ "UserManagement" and OperationName =~ "Delete user"
| mv-expand TargetResource = TargetResources
| where TargetResource["type"] == "User" and TargetResource["userPrincipalName"] has "#EXT#"
| extend ParsedDeletedUserPrincipalName = extract(@"^[0-9a-f]{32}([^\#]+)\#EXT\#", 1, tostring(TargetResource["userPrincipalName"]))
| extend
    Initiator = iif(isnotempty(InitiatedBy["app"]), tostring(InitiatedBy["app"]["displayName"]), tostring(InitiatedBy["user"]["userPrincipalName"])),
    InitiatorId = iif(isnotempty(InitiatedBy["app"]), tostring(InitiatedBy["app"]["servicePrincipalId"]), tostring(InitiatedBy["user"]["id"])),
    Delete_IPAddress = tostring(InitiatedBy[tostring(bag_keys(InitiatedBy)[0])]["ipAddress"])
| project Delete_TimeGenerated = TimeGenerated, Category, Identity, Initiator, Delete_IPAddress, OperationName, Result, ParsedDeletedUserPrincipalName, InitiatedBy, AdditionalDetails, TargetResources, InitiatorId, CorrelationId
| join kind=inner (
    SigninLogs
    | where TimeGenerated > ago(query_period)
    | where ResultType == 0
    | summarize take_any(*) by UserPrincipalName
    | extend ParsedUserPrincipalName = translate("@", "_", UserPrincipalName)
    | project SigninLogs_TimeGenerated = TimeGenerated, UserPrincipalName, UserDisplayName, ResultType, ResultDescription, IPAddress, LocationDetails, AppDisplayName, ResourceDisplayName, ClientAppUsed, UserAgent, DeviceDetail, UserId, UserType, OriginalRequestId, ParsedUserPrincipalName
    ) on $left.ParsedDeletedUserPrincipalName == $right.ParsedUserPrincipalName
| where SigninLogs_TimeGenerated > Delete_TimeGenerated
| project-away ParsedDeletedUserPrincipalName, ParsedUserPrincipalName
| extend
    AccountName = tostring(split(UserPrincipalName, "@")[0]),
    AccountUPNSuffix = tostring(split(UserPrincipalName, "@")[1])

YAML

description: |
  ' This query will detect logins from guest account which was recently deleted. 
  For any successful logins from deleted identities should be investigated further if any existing user accounts have been altered or linked to such identity prior deletion'  
queryPeriod: 1d
severity: Medium
tags:
- GuestorExternalIdentities
triggerThreshold: 0
queryFrequency: 1h
tactics:
- PrivilegeEscalation
version: 1.0.5
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/MultipleDataSources/SuspiciousLoginfromDeletedExternalIdentities.yaml
query: |
  let query_frequency = 1h;
  let query_period = 1d;
  AuditLogs
  | where TimeGenerated > ago(query_frequency)
  | where Category =~ "UserManagement" and OperationName =~ "Delete user"
  | mv-expand TargetResource = TargetResources
  | where TargetResource["type"] == "User" and TargetResource["userPrincipalName"] has "#EXT#"
  | extend ParsedDeletedUserPrincipalName = extract(@"^[0-9a-f]{32}([^\#]+)\#EXT\#", 1, tostring(TargetResource["userPrincipalName"]))
  | extend
      Initiator = iif(isnotempty(InitiatedBy["app"]), tostring(InitiatedBy["app"]["displayName"]), tostring(InitiatedBy["user"]["userPrincipalName"])),
      InitiatorId = iif(isnotempty(InitiatedBy["app"]), tostring(InitiatedBy["app"]["servicePrincipalId"]), tostring(InitiatedBy["user"]["id"])),
      Delete_IPAddress = tostring(InitiatedBy[tostring(bag_keys(InitiatedBy)[0])]["ipAddress"])
  | project Delete_TimeGenerated = TimeGenerated, Category, Identity, Initiator, Delete_IPAddress, OperationName, Result, ParsedDeletedUserPrincipalName, InitiatedBy, AdditionalDetails, TargetResources, InitiatorId, CorrelationId
  | join kind=inner (
      SigninLogs
      | where TimeGenerated > ago(query_period)
      | where ResultType == 0
      | summarize take_any(*) by UserPrincipalName
      | extend ParsedUserPrincipalName = translate("@", "_", UserPrincipalName)
      | project SigninLogs_TimeGenerated = TimeGenerated, UserPrincipalName, UserDisplayName, ResultType, ResultDescription, IPAddress, LocationDetails, AppDisplayName, ResourceDisplayName, ClientAppUsed, UserAgent, DeviceDetail, UserId, UserType, OriginalRequestId, ParsedUserPrincipalName
      ) on $left.ParsedDeletedUserPrincipalName == $right.ParsedUserPrincipalName
  | where SigninLogs_TimeGenerated > Delete_TimeGenerated
  | project-away ParsedDeletedUserPrincipalName, ParsedUserPrincipalName
  | extend
      AccountName = tostring(split(UserPrincipalName, "@")[0]),
      AccountUPNSuffix = tostring(split(UserPrincipalName, "@")[1])  
metadata:
  categories:
    domains:
    - Security - Others
    - Identity
  author:
    name: Microsoft Security Research
  source:
    kind: Community
  support:
    tier: Community
triggerOperator: gt
name: Suspicious Login from deleted guest account
requiredDataConnectors:
- connectorId: AzureActiveDirectory
  dataTypes:
  - AuditLogs
- connectorId: AzureActiveDirectory
  dataTypes:
  - SigninLogs
relevantTechniques:
- T1078.004
kind: Scheduled
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: UserPrincipalName
  - identifier: Name
    columnName: AccountName
  - identifier: UPNSuffix
    columnName: AccountUPNSuffix
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: IPAddress
id: defe4855-0d33-4362-9557-009237623976

ARM