GSA Enriched Office 365 - Mail Redirect via ExO Transport Rule

// OfficeActivity Query
let officeActivityQuery = 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 = tostring(ExpandedParameters.Value)  // Cast to string
    | extend ClientIPValues = extract_all(@'\[?(::ffff:)?(?P<IPAddress>(\d+\.\d+\.\d+\.\d+)|[^\]]+)\]?([-:](?P<Port>\d+))?', dynamic(["IPAddress", "Port"]), ClientIP)[0]
    | extend From = ParsedParameters.From
    | project
        TimeGenerated,
        RedirectTo,
        IPAddress = tostring(ClientIPValues[0]),
        Port = tostring(ClientIPValues[1]),
        UserId,
        From,
        Operation,
        RuleName,
        Parameters
    | extend
        AccountName = tostring(split(UserId, "@")[0]),
        AccountUPNSuffix = tostring(split(UserId, "@")[1]);
    // EnrichedMicrosoft365AuditLogs Query
    let enrichedLogsQuery = EnrichedMicrosoft365AuditLogs
    | where Workload == "Exchange"
    | where Operation in~ ("New-TransportRule", "Set-TransportRule")
    | extend AdditionalProps = parse_json(AdditionalProperties)
    | mv-apply DynamicParameters = todynamic(AdditionalProps.Parameters) on (
        summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value))
    )
    | extend RuleName = case(
        Operation =~ "Set-TransportRule", ObjectId,
        Operation =~ "New-TransportRule", ParsedParameters.Name,
        "Unknown"
    )
    | mv-expand ExpandedParameters = todynamic(AdditionalProps.Parameters)
    | where ExpandedParameters.Name in~ ("BlindCopyTo", "RedirectMessageTo") and isnotempty(ExpandedParameters.Value)
    | extend RedirectTo = tostring(ExpandedParameters.Value)  // Cast to string
    | extend ClientIPValues = extract_all(@'\[?(::ffff:)?(?P<IPAddress>(\d+\.\d+\.\d+\.\d+)|[^\]]+)\]?([-:](?P<Port>\d+))?', dynamic(["IPAddress", "Port"]), ClientIp)[0]
    | extend From = ParsedParameters.From
    | extend UserAgent = tostring(AdditionalProps.UserAgent)
    | project
        TimeGenerated,
        RedirectTo,
        IPAddress = tostring(ClientIPValues[0]),
        Port = tostring(ClientIPValues[1]),
        UserId,
        From,
        Operation,
        RuleName,
        Parameters = tostring(AdditionalProps.Parameters),
        UserAgent
    | extend
        AccountName = tostring(split(UserId, "@")[0]),
        AccountUPNSuffix = tostring(split(UserId, "@")[1]);
    // Combine both queries
    union isfuzzy=true officeActivityQuery, enrichedLogsQuery
    | summarize arg_min(TimeGenerated, *) by RuleName, RedirectTo
    | project
        TimeGenerated,
        RedirectTo,
        IPAddress,
        Port,
        UserId,
        From,
        Operation,
        RuleName,
        Parameters,
        AccountName,
        AccountUPNSuffix
        | order by TimeGenerated desc

relevantTechniques:
- T1114
- T1020
name: GSA Enriched Office 365 - Mail Redirect via ExO Transport Rule
requiredDataConnectors:
- dataTypes:
  - OfficeActivity (Exchange)
  connectorId: Office365
- dataTypes:
  - EnrichedMicrosoft365AuditLogs
  connectorId: AzureActiveDirectory
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: UserId
  - identifier: Name
    columnName: AccountName
  - identifier: UPNSuffix
    columnName: AccountUPNSuffix
  entityType: Account
- fieldMappings:
  - identifier: Address
    columnName: IPAddress
  entityType: IP
triggerThreshold: 0
id: edcfc2e0-3134-434c-8074-9101c530d419
tactics:
- Collection
- Exfiltration
version: 2.1.5
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Global Secure Access/Analytic Rules/Office 365 - Mail_redirect_via_ExO_transport_rule.yaml
queryPeriod: 1h
kind: Scheduled
queryFrequency: 1h
severity: Medium
status: Available
description: |
  Identifies when an Exchange Online transport rule is configured to forward emails.
  This could indicate an adversary mailbox configured to collect mail from multiple user accounts.  
query: |
  // OfficeActivity Query
  let officeActivityQuery = 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 = tostring(ExpandedParameters.Value)  // Cast to string
      | extend ClientIPValues = extract_all(@'\[?(::ffff:)?(?P<IPAddress>(\d+\.\d+\.\d+\.\d+)|[^\]]+)\]?([-:](?P<Port>\d+))?', dynamic(["IPAddress", "Port"]), ClientIP)[0]
      | extend From = ParsedParameters.From
      | project
          TimeGenerated,
          RedirectTo,
          IPAddress = tostring(ClientIPValues[0]),
          Port = tostring(ClientIPValues[1]),
          UserId,
          From,
          Operation,
          RuleName,
          Parameters
      | extend
          AccountName = tostring(split(UserId, "@")[0]),
          AccountUPNSuffix = tostring(split(UserId, "@")[1]);
      // EnrichedMicrosoft365AuditLogs Query
      let enrichedLogsQuery = EnrichedMicrosoft365AuditLogs
      | where Workload == "Exchange"
      | where Operation in~ ("New-TransportRule", "Set-TransportRule")
      | extend AdditionalProps = parse_json(AdditionalProperties)
      | mv-apply DynamicParameters = todynamic(AdditionalProps.Parameters) on (
          summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value))
      )
      | extend RuleName = case(
          Operation =~ "Set-TransportRule", ObjectId,
          Operation =~ "New-TransportRule", ParsedParameters.Name,
          "Unknown"
      )
      | mv-expand ExpandedParameters = todynamic(AdditionalProps.Parameters)
      | where ExpandedParameters.Name in~ ("BlindCopyTo", "RedirectMessageTo") and isnotempty(ExpandedParameters.Value)
      | extend RedirectTo = tostring(ExpandedParameters.Value)  // Cast to string
      | extend ClientIPValues = extract_all(@'\[?(::ffff:)?(?P<IPAddress>(\d+\.\d+\.\d+\.\d+)|[^\]]+)\]?([-:](?P<Port>\d+))?', dynamic(["IPAddress", "Port"]), ClientIp)[0]
      | extend From = ParsedParameters.From
      | extend UserAgent = tostring(AdditionalProps.UserAgent)
      | project
          TimeGenerated,
          RedirectTo,
          IPAddress = tostring(ClientIPValues[0]),
          Port = tostring(ClientIPValues[1]),
          UserId,
          From,
          Operation,
          RuleName,
          Parameters = tostring(AdditionalProps.Parameters),
          UserAgent
      | extend
          AccountName = tostring(split(UserId, "@")[0]),
          AccountUPNSuffix = tostring(split(UserId, "@")[1]);
      // Combine both queries
      union isfuzzy=true officeActivityQuery, enrichedLogsQuery
      | summarize arg_min(TimeGenerated, *) by RuleName, RedirectTo
      | project
          TimeGenerated,
          RedirectTo,
          IPAddress,
          Port,
          UserId,
          From,
          Operation,
          RuleName,
          Parameters,
          AccountName,
          AccountUPNSuffix
          | order by TimeGenerated desc  
triggerOperator: gt

{
  "$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/edcfc2e0-3134-434c-8074-9101c530d419')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/edcfc2e0-3134-434c-8074-9101c530d419')]",
      "properties": {
        "alertRuleTemplateName": "edcfc2e0-3134-434c-8074-9101c530d419",
        "customDetails": null,
        "description": "Identifies when an Exchange Online transport rule is configured to forward emails.\nThis could indicate an adversary mailbox configured to collect mail from multiple user accounts.\n",
        "displayName": "GSA Enriched Office 365 - Mail Redirect via ExO Transport Rule",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "UserId",
                "identifier": "FullName"
              },
              {
                "columnName": "AccountName",
                "identifier": "Name"
              },
              {
                "columnName": "AccountUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "IPAddress",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Global Secure Access/Analytic Rules/Office 365 - Mail_redirect_via_ExO_transport_rule.yaml",
        "query": "// OfficeActivity Query\nlet officeActivityQuery = OfficeActivity\n    | where OfficeWorkload == \"Exchange\"\n    | where Operation in~ (\"New-TransportRule\", \"Set-TransportRule\")\n    | mv-apply DynamicParameters = todynamic(Parameters) on (\n        summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value))\n    )\n    | extend RuleName = case(\n        Operation =~ \"Set-TransportRule\", OfficeObjectId,\n        Operation =~ \"New-TransportRule\", ParsedParameters.Name,\n        \"Unknown\"\n    )\n    | mv-expand ExpandedParameters = todynamic(Parameters)\n    | where ExpandedParameters.Name in~ (\"BlindCopyTo\", \"RedirectMessageTo\") and isnotempty(ExpandedParameters.Value)\n    | extend RedirectTo = tostring(ExpandedParameters.Value)  // Cast to string\n    | extend ClientIPValues = extract_all(@'\\[?(::ffff:)?(?P<IPAddress>(\\d+\\.\\d+\\.\\d+\\.\\d+)|[^\\]]+)\\]?([-:](?P<Port>\\d+))?', dynamic([\"IPAddress\", \"Port\"]), ClientIP)[0]\n    | extend From = ParsedParameters.From\n    | project\n        TimeGenerated,\n        RedirectTo,\n        IPAddress = tostring(ClientIPValues[0]),\n        Port = tostring(ClientIPValues[1]),\n        UserId,\n        From,\n        Operation,\n        RuleName,\n        Parameters\n    | extend\n        AccountName = tostring(split(UserId, \"@\")[0]),\n        AccountUPNSuffix = tostring(split(UserId, \"@\")[1]);\n    // EnrichedMicrosoft365AuditLogs Query\n    let enrichedLogsQuery = EnrichedMicrosoft365AuditLogs\n    | where Workload == \"Exchange\"\n    | where Operation in~ (\"New-TransportRule\", \"Set-TransportRule\")\n    | extend AdditionalProps = parse_json(AdditionalProperties)\n    | mv-apply DynamicParameters = todynamic(AdditionalProps.Parameters) on (\n        summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value))\n    )\n    | extend RuleName = case(\n        Operation =~ \"Set-TransportRule\", ObjectId,\n        Operation =~ \"New-TransportRule\", ParsedParameters.Name,\n        \"Unknown\"\n    )\n    | mv-expand ExpandedParameters = todynamic(AdditionalProps.Parameters)\n    | where ExpandedParameters.Name in~ (\"BlindCopyTo\", \"RedirectMessageTo\") and isnotempty(ExpandedParameters.Value)\n    | extend RedirectTo = tostring(ExpandedParameters.Value)  // Cast to string\n    | extend ClientIPValues = extract_all(@'\\[?(::ffff:)?(?P<IPAddress>(\\d+\\.\\d+\\.\\d+\\.\\d+)|[^\\]]+)\\]?([-:](?P<Port>\\d+))?', dynamic([\"IPAddress\", \"Port\"]), ClientIp)[0]\n    | extend From = ParsedParameters.From\n    | extend UserAgent = tostring(AdditionalProps.UserAgent)\n    | project\n        TimeGenerated,\n        RedirectTo,\n        IPAddress = tostring(ClientIPValues[0]),\n        Port = tostring(ClientIPValues[1]),\n        UserId,\n        From,\n        Operation,\n        RuleName,\n        Parameters = tostring(AdditionalProps.Parameters),\n        UserAgent\n    | extend\n        AccountName = tostring(split(UserId, \"@\")[0]),\n        AccountUPNSuffix = tostring(split(UserId, \"@\")[1]);\n    // Combine both queries\n    union isfuzzy=true officeActivityQuery, enrichedLogsQuery\n    | summarize arg_min(TimeGenerated, *) by RuleName, RedirectTo\n    | project\n        TimeGenerated,\n        RedirectTo,\n        IPAddress,\n        Port,\n        UserId,\n        From,\n        Operation,\n        RuleName,\n        Parameters,\n        AccountName,\n        AccountUPNSuffix\n        | order by TimeGenerated desc\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Collection",
          "Exfiltration"
        ],
        "techniques": [
          "T1020",
          "T1114"
        ],
        "templateVersion": "2.1.5",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}