Microsoft Sentinel Analytic Rules
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External guest invitation followed by Azure AD PowerShell signin

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Idacc4c247-aaf7-494b-b5da-17f18863878a
RulenameExternal guest invitation followed by Azure AD PowerShell signin
DescriptionBy default guests have capability to invite more external guest users, guests also can do suspicious Azure AD enumeration. This detection look at guests

users, who have been invited or have invited recently, who also are logging via various PowerShell CLI.

Ref : ‘https://danielchronlund.com/2021/11/18/scary-azure-ad-tenant-enumeration-using-regular-b2b-guest-accounts/
SeverityMedium
TacticsInitialAccess
Persistence
Discovery
TechniquesT1078.004
T1136.003
T1087.004
Required data connectorsAzureActiveDirectory
KindScheduled
Query frequency1h
Query period1d
Trigger threshold0
Trigger operatorgt
Source Urihttps://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure Active Directory/Analytic Rules/UnusualGuestActivity.yaml
Version1.0.7
Arm templateacc4c247-aaf7-494b-b5da-17f18863878a.json
Deploy To Azure
let queryfrequency = 1h;
let queryperiod = 1d;
AuditLogs
| where TimeGenerated > ago(queryperiod)
| where OperationName in ("Invite external user", "Bulk invite users - started (bulk)", "Invite external user with reset invitation status")
| extend InitiatedBy = iff(isnotempty(InitiatedBy.user.userPrincipalName), InitiatedBy.user.userPrincipalName, InitiatedBy.app.displayName)
// Uncomment the following line to filter events where the inviting user was a guest user
//| where InitiatedBy has_any ("live.com#", "#EXT#")
| mv-apply TargetResource = TargetResources on 
  (
      where TargetResource.type =~ "User"
      | extend InvitedUser = tostring(TargetResource.userPrincipalName)
  )
| mv-expand UserToCompare = pack_array(InitiatedBy, InvitedUser) to typeof(string)
| where UserToCompare has_any ("live.com#", "#EXT#")
| extend
    parsedUser = replace_string(tolower(iff(UserToCompare startswith "live.com#", tostring(split(UserToCompare, "#")[1]), tostring(split(UserToCompare, "#EXT#")[0]))), "@", "_"),
    InvitationTime = TimeGenerated
| join (
    (union isfuzzy=true SigninLogs, AADNonInteractiveUserSignInLogs)
    | where TimeGenerated > ago(queryfrequency)
    | where UserType != "Member"
    | where AppId has_any                       // This web may contain a list of these apps: https://msshells.net/
        ("1b730954-1685-4b74-9bfd-dac224a7b894",// Azure Active Directory PowerShell
         "04b07795-8ddb-461a-bbee-02f9e1bf7b46",// Microsoft Azure CLI
         "1950a258-227b-4e31-a9cf-717495945fc2",// Microsoft Azure PowerShell
         "a0c73c16-a7e3-4564-9a95-2bdf47383716",// Microsoft Exchange Online Remote PowerShell
         "fb78d390-0c51-40cd-8e17-fdbfab77341b",// Microsoft Exchange REST API Based Powershell
         "d1ddf0e4-d672-4dae-b554-9d5bdfd93547",// Microsoft Intune PowerShell
         "9bc3ab49-b65d-410a-85ad-de819febfddc",// Microsoft SharePoint Online Management Shell
         "12128f48-ec9e-42f0-b203-ea49fb6af367",// MS Teams Powershell Cmdlets
         "23d8f6bd-1eb0-4cc2-a08c-7bf525c67bcd",// Power BI PowerShell
         "31359c7f-bd7e-475c-86db-fdb8c937548e",// PnP Management Shell
         "90f610bf-206d-4950-b61d-37fa6fd1b224",// Aadrm Admin Powershell
         "14d82eec-204b-4c2f-b7e8-296a70dab67e" // Microsoft Graph PowerShell
        )
    | summarize arg_min(TimeGenerated, *) by UserPrincipalName
    | extend
        parsedUser = replace_string(UserPrincipalName, "@", "_"),
        SigninTime = TimeGenerated
    )
    on parsedUser
| project InvitationTime, InitiatedBy, OperationName, InvitedUser, SigninTime, SigninCategory = Category1, SigninUserPrincipalName = UserPrincipalName, IPAddress, AppDisplayName, ResourceDisplayName, UserAgent, InvitationAdditionalDetails = AdditionalDetails, InvitationTargetResources = TargetResources
| extend InvitedUserName = tostring(split(InvitedUser,'@',0)[0]), InvitedUserUPNSuffix = tostring(split(InvitedUser,'@',1)[0]), 
         InitiatedByName = tostring(split(InitiatedBy,'@',0)[0]), InitiatedByUPNSuffix = tostring(split(InitiatedBy,'@',1)[0])

severity: Medium
triggerThreshold: 0
query: |
  let queryfrequency = 1h;
  let queryperiod = 1d;
  AuditLogs
  | where TimeGenerated > ago(queryperiod)
  | where OperationName in ("Invite external user", "Bulk invite users - started (bulk)", "Invite external user with reset invitation status")
  | extend InitiatedBy = iff(isnotempty(InitiatedBy.user.userPrincipalName), InitiatedBy.user.userPrincipalName, InitiatedBy.app.displayName)
  // Uncomment the following line to filter events where the inviting user was a guest user
  //| where InitiatedBy has_any ("live.com#", "#EXT#")
  | mv-apply TargetResource = TargetResources on 
    (
        where TargetResource.type =~ "User"
        | extend InvitedUser = tostring(TargetResource.userPrincipalName)
    )
  | mv-expand UserToCompare = pack_array(InitiatedBy, InvitedUser) to typeof(string)
  | where UserToCompare has_any ("live.com#", "#EXT#")
  | extend
      parsedUser = replace_string(tolower(iff(UserToCompare startswith "live.com#", tostring(split(UserToCompare, "#")[1]), tostring(split(UserToCompare, "#EXT#")[0]))), "@", "_"),
      InvitationTime = TimeGenerated
  | join (
      (union isfuzzy=true SigninLogs, AADNonInteractiveUserSignInLogs)
      | where TimeGenerated > ago(queryfrequency)
      | where UserType != "Member"
      | where AppId has_any                       // This web may contain a list of these apps: https://msshells.net/
          ("1b730954-1685-4b74-9bfd-dac224a7b894",// Azure Active Directory PowerShell
           "04b07795-8ddb-461a-bbee-02f9e1bf7b46",// Microsoft Azure CLI
           "1950a258-227b-4e31-a9cf-717495945fc2",// Microsoft Azure PowerShell
           "a0c73c16-a7e3-4564-9a95-2bdf47383716",// Microsoft Exchange Online Remote PowerShell
           "fb78d390-0c51-40cd-8e17-fdbfab77341b",// Microsoft Exchange REST API Based Powershell
           "d1ddf0e4-d672-4dae-b554-9d5bdfd93547",// Microsoft Intune PowerShell
           "9bc3ab49-b65d-410a-85ad-de819febfddc",// Microsoft SharePoint Online Management Shell
           "12128f48-ec9e-42f0-b203-ea49fb6af367",// MS Teams Powershell Cmdlets
           "23d8f6bd-1eb0-4cc2-a08c-7bf525c67bcd",// Power BI PowerShell
           "31359c7f-bd7e-475c-86db-fdb8c937548e",// PnP Management Shell
           "90f610bf-206d-4950-b61d-37fa6fd1b224",// Aadrm Admin Powershell
           "14d82eec-204b-4c2f-b7e8-296a70dab67e" // Microsoft Graph PowerShell
          )
      | summarize arg_min(TimeGenerated, *) by UserPrincipalName
      | extend
          parsedUser = replace_string(UserPrincipalName, "@", "_"),
          SigninTime = TimeGenerated
      )
      on parsedUser
  | project InvitationTime, InitiatedBy, OperationName, InvitedUser, SigninTime, SigninCategory = Category1, SigninUserPrincipalName = UserPrincipalName, IPAddress, AppDisplayName, ResourceDisplayName, UserAgent, InvitationAdditionalDetails = AdditionalDetails, InvitationTargetResources = TargetResources
  | extend InvitedUserName = tostring(split(InvitedUser,'@',0)[0]), InvitedUserUPNSuffix = tostring(split(InvitedUser,'@',1)[0]), 
           InitiatedByName = tostring(split(InitiatedBy,'@',0)[0]), InitiatedByUPNSuffix = tostring(split(InitiatedBy,'@',1)[0])  
queryFrequency: 1h
requiredDataConnectors:
- connectorId: AzureActiveDirectory
  dataTypes:
  - AuditLogs
- connectorId: AzureActiveDirectory
  dataTypes:
  - SigninLogs
id: acc4c247-aaf7-494b-b5da-17f18863878a
version: 1.0.7
name: External guest invitation followed by Azure AD PowerShell signin
kind: Scheduled
status: Available
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure Active Directory/Analytic Rules/UnusualGuestActivity.yaml
queryPeriod: 1d
relevantTechniques:
- T1078.004
- T1136.003
- T1087.004
triggerOperator: gt
tactics:
- InitialAccess
- Persistence
- Discovery
description: |
  'By default guests have capability to invite more external guest users, guests also can do suspicious Azure AD enumeration. This detection look at guests
  users, who have been invited or have invited recently, who also are logging via various PowerShell CLI.
  Ref : 'https://danielchronlund.com/2021/11/18/scary-azure-ad-tenant-enumeration-using-regular-b2b-guest-accounts/'  
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: Name
    columnName: InvitedUserName
  - identifier: UPNSuffix
    columnName: InvitedUserUPNSuffix
- entityType: Account
  fieldMappings:
  - identifier: Name
    columnName: InitiatedByName
  - identifier: UPNSuffix
    columnName: InitiatedByUPNSuffix
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: IPAddress

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/acc4c247-aaf7-494b-b5da-17f18863878a')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/acc4c247-aaf7-494b-b5da-17f18863878a')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01",
      "properties": {
        "displayName": "External guest invitation followed by Azure AD PowerShell signin",
        "description": "'By default guests have capability to invite more external guest users, guests also can do suspicious Azure AD enumeration. This detection look at guests\nusers, who have been invited or have invited recently, who also are logging via various PowerShell CLI.\nRef : 'https://danielchronlund.com/2021/11/18/scary-azure-ad-tenant-enumeration-using-regular-b2b-guest-accounts/'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "let queryfrequency = 1h;\nlet queryperiod = 1d;\nAuditLogs\n| where TimeGenerated > ago(queryperiod)\n| where OperationName in (\"Invite external user\", \"Bulk invite users - started (bulk)\", \"Invite external user with reset invitation status\")\n| extend InitiatedBy = iff(isnotempty(InitiatedBy.user.userPrincipalName), InitiatedBy.user.userPrincipalName, InitiatedBy.app.displayName)\n// Uncomment the following line to filter events where the inviting user was a guest user\n//| where InitiatedBy has_any (\"live.com#\", \"#EXT#\")\n| mv-apply TargetResource = TargetResources on \n  (\n      where TargetResource.type =~ \"User\"\n      | extend InvitedUser = tostring(TargetResource.userPrincipalName)\n  )\n| mv-expand UserToCompare = pack_array(InitiatedBy, InvitedUser) to typeof(string)\n| where UserToCompare has_any (\"live.com#\", \"#EXT#\")\n| extend\n    parsedUser = replace_string(tolower(iff(UserToCompare startswith \"live.com#\", tostring(split(UserToCompare, \"#\")[1]), tostring(split(UserToCompare, \"#EXT#\")[0]))), \"@\", \"_\"),\n    InvitationTime = TimeGenerated\n| join (\n    (union isfuzzy=true SigninLogs, AADNonInteractiveUserSignInLogs)\n    | where TimeGenerated > ago(queryfrequency)\n    | where UserType != \"Member\"\n    | where AppId has_any                       // This web may contain a list of these apps: https://msshells.net/\n        (\"1b730954-1685-4b74-9bfd-dac224a7b894\",// Azure Active Directory PowerShell\n         \"04b07795-8ddb-461a-bbee-02f9e1bf7b46\",// Microsoft Azure CLI\n         \"1950a258-227b-4e31-a9cf-717495945fc2\",// Microsoft Azure PowerShell\n         \"a0c73c16-a7e3-4564-9a95-2bdf47383716\",// Microsoft Exchange Online Remote PowerShell\n         \"fb78d390-0c51-40cd-8e17-fdbfab77341b\",// Microsoft Exchange REST API Based Powershell\n         \"d1ddf0e4-d672-4dae-b554-9d5bdfd93547\",// Microsoft Intune PowerShell\n         \"9bc3ab49-b65d-410a-85ad-de819febfddc\",// Microsoft SharePoint Online Management Shell\n         \"12128f48-ec9e-42f0-b203-ea49fb6af367\",// MS Teams Powershell Cmdlets\n         \"23d8f6bd-1eb0-4cc2-a08c-7bf525c67bcd\",// Power BI PowerShell\n         \"31359c7f-bd7e-475c-86db-fdb8c937548e\",// PnP Management Shell\n         \"90f610bf-206d-4950-b61d-37fa6fd1b224\",// Aadrm Admin Powershell\n         \"14d82eec-204b-4c2f-b7e8-296a70dab67e\" // Microsoft Graph PowerShell\n        )\n    | summarize arg_min(TimeGenerated, *) by UserPrincipalName\n    | extend\n        parsedUser = replace_string(UserPrincipalName, \"@\", \"_\"),\n        SigninTime = TimeGenerated\n    )\n    on parsedUser\n| project InvitationTime, InitiatedBy, OperationName, InvitedUser, SigninTime, SigninCategory = Category1, SigninUserPrincipalName = UserPrincipalName, IPAddress, AppDisplayName, ResourceDisplayName, UserAgent, InvitationAdditionalDetails = AdditionalDetails, InvitationTargetResources = TargetResources\n| extend InvitedUserName = tostring(split(InvitedUser,'@',0)[0]), InvitedUserUPNSuffix = tostring(split(InvitedUser,'@',1)[0]), \n         InitiatedByName = tostring(split(InitiatedBy,'@',0)[0]), InitiatedByUPNSuffix = tostring(split(InitiatedBy,'@',1)[0])\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "P1D",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess",
          "Persistence",
          "Discovery"
        ],
        "techniques": [
          "T1078.004",
          "T1136.003",
          "T1087.004"
        ],
        "alertRuleTemplateName": "acc4c247-aaf7-494b-b5da-17f18863878a",
        "customDetails": null,
        "entityMappings": [
          {
            "fieldMappings": [
              {
                "columnName": "InvitedUserName",
                "identifier": "Name"
              },
              {
                "columnName": "InvitedUserUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ],
            "entityType": "Account"
          },
          {
            "fieldMappings": [
              {
                "columnName": "InitiatedByName",
                "identifier": "Name"
              },
              {
                "columnName": "InitiatedByUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ],
            "entityType": "Account"
          },
          {
            "fieldMappings": [
              {
                "columnName": "IPAddress",
                "identifier": "Address"
              }
            ],
            "entityType": "IP"
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure Active Directory/Analytic Rules/UnusualGuestActivity.yaml",
        "templateVersion": "1.0.7",
        "status": "Available"
      }
    }
  ]
}