Mail redirect via ExO transport rule

OfficeActivity
| where OfficeWorkload == "Exchange"
| where Operation in~ ("New-TransportRule", "Set-TransportRule")
| mv-apply DynamicParameters = todynamic(Parameters) on (summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value)))
| extend RuleName = case(
    Operation =~ "Set-TransportRule", OfficeObjectId,
    Operation =~ "New-TransportRule", ParsedParameters.Name,
    "Unknown")
| mv-expand ExpandedParameters = todynamic(Parameters)
| where ExpandedParameters.Name in~ ("BlindCopyTo", "RedirectMessageTo") and isnotempty(ExpandedParameters.Value)
| extend RedirectTo = ExpandedParameters.Value
| extend ClientIPValues = extract_all(@'\[?(::ffff:)?(?P<IPAddress>(\d+\.\d+\.\d+\.\d+)|[^\]]+)\]?([-:](?P<Port>\d+))?', dynamic(["IPAddress", "Port"]), ClientIP)[0]
| project TimeGenerated, RedirectTo, IPAddress = tostring(ClientIPValues[0]), Port = tostring(ClientIPValues[1]), UserId, Operation, RuleName, Parameters
| extend timestamp = TimeGenerated, AccountCustomEntity = UserId, IPCustomEntity = IPAddress
    

kind: Scheduled
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft 365/Analytic Rules/Mail_redirect_via_ExO_transport_rule.yaml
severity: Medium
name: Mail redirect via ExO transport rule
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: AccountCustomEntity
    identifier: FullName
- entityType: IP
  fieldMappings:
  - columnName: IPCustomEntity
    identifier: Address
relevantTechniques:
- T1114
- T1020
queryFrequency: 1d
triggerThreshold: 0
queryPeriod: 1d
description: |
  'Identifies when Exchange Online transport rule configured to forward emails.
  This could be an adversary mailbox configured to collect mail from multiple user accounts.'  
id: 500415fb-bba7-4227-a08a-9857fb61b6a7
version: 2.0.0
tactics:
- Collection
- Exfiltration
query: "OfficeActivity\n| where OfficeWorkload == \"Exchange\"\n| where Operation in~ (\"New-TransportRule\", \"Set-TransportRule\")\n| mv-apply DynamicParameters = todynamic(Parameters) on (summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value)))\n| extend RuleName = case(\n    Operation =~ \"Set-TransportRule\", OfficeObjectId,\n    Operation =~ \"New-TransportRule\", ParsedParameters.Name,\n    \"Unknown\")\n| mv-expand ExpandedParameters = todynamic(Parameters)\n| where ExpandedParameters.Name in~ (\"BlindCopyTo\", \"RedirectMessageTo\") and isnotempty(ExpandedParameters.Value)\n| extend RedirectTo = ExpandedParameters.Value\n| extend ClientIPValues = extract_all(@'\\[?(::ffff:)?(?P<IPAddress>(\\d+\\.\\d+\\.\\d+\\.\\d+)|[^\\]]+)\\]?([-:](?P<Port>\\d+))?', dynamic([\"IPAddress\", \"Port\"]), ClientIP)[0]\n| project TimeGenerated, RedirectTo, IPAddress = tostring(ClientIPValues[0]), Port = tostring(ClientIPValues[1]), UserId, Operation, RuleName, Parameters\n| extend timestamp = TimeGenerated, AccountCustomEntity = UserId, IPCustomEntity = IPAddress\n    \n"
status: Available
requiredDataConnectors:
- dataTypes:
  - OfficeActivity
  connectorId: Office365
triggerOperator: gt

{
  "$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/500415fb-bba7-4227-a08a-9857fb61b6a7')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/500415fb-bba7-4227-a08a-9857fb61b6a7')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01-preview",
      "properties": {
        "displayName": "Mail redirect via ExO transport rule",
        "description": "'Identifies when Exchange Online transport rule configured to forward emails.\nThis could be an adversary mailbox configured to collect mail from multiple user accounts.'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "OfficeActivity\n| where OfficeWorkload == \"Exchange\"\n| where Operation in~ (\"New-TransportRule\", \"Set-TransportRule\")\n| mv-apply DynamicParameters = todynamic(Parameters) on (summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value)))\n| extend RuleName = case(\n    Operation =~ \"Set-TransportRule\", OfficeObjectId,\n    Operation =~ \"New-TransportRule\", ParsedParameters.Name,\n    \"Unknown\")\n| mv-expand ExpandedParameters = todynamic(Parameters)\n| where ExpandedParameters.Name in~ (\"BlindCopyTo\", \"RedirectMessageTo\") and isnotempty(ExpandedParameters.Value)\n| extend RedirectTo = ExpandedParameters.Value\n| extend ClientIPValues = extract_all(@'\\[?(::ffff:)?(?P<IPAddress>(\\d+\\.\\d+\\.\\d+\\.\\d+)|[^\\]]+)\\]?([-:](?P<Port>\\d+))?', dynamic([\"IPAddress\", \"Port\"]), ClientIP)[0]\n| project TimeGenerated, RedirectTo, IPAddress = tostring(ClientIPValues[0]), Port = tostring(ClientIPValues[1]), UserId, Operation, RuleName, Parameters\n| extend timestamp = TimeGenerated, AccountCustomEntity = UserId, IPCustomEntity = IPAddress\n    \n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Collection",
          "Exfiltration"
        ],
        "techniques": [
          "T1114",
          "T1020"
        ],
        "alertRuleTemplateName": "500415fb-bba7-4227-a08a-9857fb61b6a7",
        "customDetails": null,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "identifier": "FullName",
                "columnName": "AccountCustomEntity"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "identifier": "Address",
                "columnName": "IPCustomEntity"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft 365/Analytic Rules/Mail_redirect_via_ExO_transport_rule.yaml",
        "status": "Available",
        "templateVersion": "2.0.0"
      }
    }
  ]
}