Multiple users email forwarded to same destination

let queryfrequency = 1d;
let queryperiod = 7d;
OfficeActivity
| where TimeGenerated > ago(queryperiod)
| where OfficeWorkload =~ "Exchange"
//| where Operation in ("Set-Mailbox", "New-InboxRule", "Set-InboxRule")
| where Parameters has_any ("ForwardTo", "RedirectTo", "ForwardingSmtpAddress")
| mv-apply DynamicParameters = todynamic(Parameters) on (summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value)))
| evaluate bag_unpack(ParsedParameters, columnsConflict='replace_source')
| extend DestinationMailAddress = tolower(case(
    isnotempty(column_ifexists("ForwardTo", "")), column_ifexists("ForwardTo", ""),
    isnotempty(column_ifexists("RedirectTo", "")), column_ifexists("RedirectTo", ""),
    isnotempty(column_ifexists("ForwardingSmtpAddress", "")), trim_start(@"smtp:", column_ifexists("ForwardingSmtpAddress", "")),
    ""))
| where isnotempty(DestinationMailAddress)
| mv-expand split(DestinationMailAddress, ";")
| extend ClientIPValues = extract_all(@'\[?(::ffff:)?(?P<IPAddress>(\d+\.\d+\.\d+\.\d+)|[^\]]+)\]?([-:](?P<Port>\d+))?', dynamic(["IPAddress", "Port"]), ClientIP)[0]
| extend ClientIP = tostring(ClientIPValues[0]), Port = tostring(ClientIPValues[1])
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), DistinctUserCount = dcount(UserId), UserId = make_set(UserId, 250), Ports = make_set(Port, 250), EventCount = count() by tostring(DestinationMailAddress), ClientIP
| where DistinctUserCount > 1 and EndTime > ago(queryfrequency)
| mv-expand UserId to typeof(string)
| extend timestamp = StartTime, AccountCustomEntity = UserId, IPCustomEntity = ClientIP

triggerThreshold: 0
queryFrequency: 1d
relevantTechniques:
- T1114
- T1020
tactics:
- Collection
- Exfiltration
id: a1551ae4-f61c-4bca-9c57-4d0d681db2e9
kind: Scheduled
triggerOperator: gt
severity: Medium
version: 2.0.0
requiredDataConnectors:
- connectorId: Office365
  dataTypes:
  - OfficeActivity
query: |
  let queryfrequency = 1d;
  let queryperiod = 7d;
  OfficeActivity
  | where TimeGenerated > ago(queryperiod)
  | where OfficeWorkload =~ "Exchange"
  //| where Operation in ("Set-Mailbox", "New-InboxRule", "Set-InboxRule")
  | where Parameters has_any ("ForwardTo", "RedirectTo", "ForwardingSmtpAddress")
  | mv-apply DynamicParameters = todynamic(Parameters) on (summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value)))
  | evaluate bag_unpack(ParsedParameters, columnsConflict='replace_source')
  | extend DestinationMailAddress = tolower(case(
      isnotempty(column_ifexists("ForwardTo", "")), column_ifexists("ForwardTo", ""),
      isnotempty(column_ifexists("RedirectTo", "")), column_ifexists("RedirectTo", ""),
      isnotempty(column_ifexists("ForwardingSmtpAddress", "")), trim_start(@"smtp:", column_ifexists("ForwardingSmtpAddress", "")),
      ""))
  | where isnotempty(DestinationMailAddress)
  | mv-expand split(DestinationMailAddress, ";")
  | extend ClientIPValues = extract_all(@'\[?(::ffff:)?(?P<IPAddress>(\d+\.\d+\.\d+\.\d+)|[^\]]+)\]?([-:](?P<Port>\d+))?', dynamic(["IPAddress", "Port"]), ClientIP)[0]
  | extend ClientIP = tostring(ClientIPValues[0]), Port = tostring(ClientIPValues[1])
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), DistinctUserCount = dcount(UserId), UserId = make_set(UserId, 250), Ports = make_set(Port, 250), EventCount = count() by tostring(DestinationMailAddress), ClientIP
  | where DistinctUserCount > 1 and EndTime > ago(queryfrequency)
  | mv-expand UserId to typeof(string)
  | extend timestamp = StartTime, AccountCustomEntity = UserId, IPCustomEntity = ClientIP  
entityMappings:
- fieldMappings:
  - columnName: AccountCustomEntity
    identifier: FullName
  entityType: Account
- fieldMappings:
  - columnName: IPCustomEntity
    identifier: Address
  entityType: IP
queryPeriod: 7d
name: Multiple users email forwarded to same destination
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft 365/Hunting Queries/MultipleUsersEmailForwardedToSameDestination.yaml
status: Available
description: |
  'Identifies when multiple (more than one) users mailboxes are configured to forward to the same destination. 
  This could be an attacker-controlled destination mailbox configured to collect mail from multiple compromised user accounts.'  

{
  "$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/a1551ae4-f61c-4bca-9c57-4d0d681db2e9')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/a1551ae4-f61c-4bca-9c57-4d0d681db2e9')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01",
      "properties": {
        "displayName": "Multiple users email forwarded to same destination",
        "description": "'Identifies when multiple (more than one) users mailboxes are configured to forward to the same destination. \nThis could be an attacker-controlled destination mailbox configured to collect mail from multiple compromised user accounts.'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "let queryfrequency = 1d;\nlet queryperiod = 7d;\nOfficeActivity\n| where TimeGenerated > ago(queryperiod)\n| where OfficeWorkload =~ \"Exchange\"\n//| where Operation in (\"Set-Mailbox\", \"New-InboxRule\", \"Set-InboxRule\")\n| where Parameters has_any (\"ForwardTo\", \"RedirectTo\", \"ForwardingSmtpAddress\")\n| mv-apply DynamicParameters = todynamic(Parameters) on (summarize ParsedParameters = make_bag(pack(tostring(DynamicParameters.Name), DynamicParameters.Value)))\n| evaluate bag_unpack(ParsedParameters, columnsConflict='replace_source')\n| extend DestinationMailAddress = tolower(case(\n    isnotempty(column_ifexists(\"ForwardTo\", \"\")), column_ifexists(\"ForwardTo\", \"\"),\n    isnotempty(column_ifexists(\"RedirectTo\", \"\")), column_ifexists(\"RedirectTo\", \"\"),\n    isnotempty(column_ifexists(\"ForwardingSmtpAddress\", \"\")), trim_start(@\"smtp:\", column_ifexists(\"ForwardingSmtpAddress\", \"\")),\n    \"\"))\n| where isnotempty(DestinationMailAddress)\n| mv-expand split(DestinationMailAddress, \";\")\n| extend ClientIPValues = extract_all(@'\\[?(::ffff:)?(?P<IPAddress>(\\d+\\.\\d+\\.\\d+\\.\\d+)|[^\\]]+)\\]?([-:](?P<Port>\\d+))?', dynamic([\"IPAddress\", \"Port\"]), ClientIP)[0]\n| extend ClientIP = tostring(ClientIPValues[0]), Port = tostring(ClientIPValues[1])\n| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), DistinctUserCount = dcount(UserId), UserId = make_set(UserId, 250), Ports = make_set(Port, 250), EventCount = count() by tostring(DestinationMailAddress), ClientIP\n| where DistinctUserCount > 1 and EndTime > ago(queryfrequency)\n| mv-expand UserId to typeof(string)\n| extend timestamp = StartTime, AccountCustomEntity = UserId, IPCustomEntity = ClientIP\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P7D",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Collection",
          "Exfiltration"
        ],
        "techniques": [
          "T1114",
          "T1020"
        ],
        "alertRuleTemplateName": "a1551ae4-f61c-4bca-9c57-4d0d681db2e9",
        "customDetails": null,
        "entityMappings": [
          {
            "fieldMappings": [
              {
                "columnName": "AccountCustomEntity",
                "identifier": "FullName"
              }
            ],
            "entityType": "Account"
          },
          {
            "fieldMappings": [
              {
                "columnName": "IPCustomEntity",
                "identifier": "Address"
              }
            ],
            "entityType": "IP"
          }
        ],
        "templateVersion": "2.0.0",
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft 365/Hunting Queries/MultipleUsersEmailForwardedToSameDestination.yaml",
        "status": "Available"
      }
    }
  ]
}