ProofpointPOD - Multiple protected emails to unknown recipient

let lbtime = 30m;
let lbperiod = 14d;
let knownrecipients = ProofpointPOD
| where TimeGenerated > ago(lbperiod)
| where EventType == 'message'
| where NetworkDirection == 'outbound'
| where SrcUserUpn != ''
| where array_length(todynamic(DstUserUpn)) == 1
| summarize recipients = make_set(tostring(todynamic(DstUserUpn)[0])) by SrcUserUpn
| extend commcol = SrcUserUpn;
ProofpointPOD
| where TimeGenerated between (ago(lbtime) .. now())
| where EventType == 'message'
| where NetworkDirection == 'outbound'
| extend isProtected = todynamic(MsgParts)[0]['isProtected']
| extend mimePgp = todynamic(MsgParts)[0]['detectedMime']
| where isProtected == 'true' or mimePgp == 'application/pgp-encrypted'
| extend DstUserMail = tostring(todynamic(DstUserUpn)[0])
| extend commcol = tostring(todynamic(DstUserUpn)[0])
| join knownrecipients on commcol
| where recipients !contains DstUserMail
| project SrcUserUpn, DstUserMail
| extend AccountCustomEntity = SrcUserUpn

triggerOperator: gt
queryFrequency: 30m
description: |
    'Detects when multiple protected messages where sent to early not seen recipient.'
status: Available
kind: Scheduled
triggerThreshold: 0
requiredDataConnectors:
- connectorId: ProofpointPOD
  dataTypes:
  - ProofpointPOD_message_CL
version: 1.1.1
queryPeriod: 30m
name: ProofpointPOD - Multiple protected emails to unknown recipient
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Proofpoint On demand(POD) Email Security/Analytic Rules/ProofpointPODMultipleProtectedEmailsToUnknownRecipient.yaml
id: f8127962-7739-4211-a4a9-390a7a00e91f
tactics:
- Exfiltration
relevantTechniques:
- T1567
severity: Medium
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: AccountCustomEntity
  entityType: Account
query: |
  let lbtime = 30m;
  let lbperiod = 14d;
  let knownrecipients = ProofpointPOD
  | where TimeGenerated > ago(lbperiod)
  | where EventType == 'message'
  | where NetworkDirection == 'outbound'
  | where SrcUserUpn != ''
  | where array_length(todynamic(DstUserUpn)) == 1
  | summarize recipients = make_set(tostring(todynamic(DstUserUpn)[0])) by SrcUserUpn
  | extend commcol = SrcUserUpn;
  ProofpointPOD
  | where TimeGenerated between (ago(lbtime) .. now())
  | where EventType == 'message'
  | where NetworkDirection == 'outbound'
  | extend isProtected = todynamic(MsgParts)[0]['isProtected']
  | extend mimePgp = todynamic(MsgParts)[0]['detectedMime']
  | where isProtected == 'true' or mimePgp == 'application/pgp-encrypted'
  | extend DstUserMail = tostring(todynamic(DstUserUpn)[0])
  | extend commcol = tostring(todynamic(DstUserUpn)[0])
  | join knownrecipients on commcol
  | where recipients !contains DstUserMail
  | project SrcUserUpn, DstUserMail
  | extend AccountCustomEntity = SrcUserUpn  

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2023-02-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/f8127962-7739-4211-a4a9-390a7a00e91f')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/f8127962-7739-4211-a4a9-390a7a00e91f')]",
      "properties": {
        "alertRuleTemplateName": "f8127962-7739-4211-a4a9-390a7a00e91f",
        "customDetails": null,
        "description": "'Detects when multiple protected messages where sent to early not seen recipient.'\n",
        "displayName": "ProofpointPOD - Multiple protected emails to unknown recipient",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "AccountCustomEntity",
                "identifier": "FullName"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Proofpoint On demand(POD) Email Security/Analytic Rules/ProofpointPODMultipleProtectedEmailsToUnknownRecipient.yaml",
        "query": "let lbtime = 30m;\nlet lbperiod = 14d;\nlet knownrecipients = ProofpointPOD\n| where TimeGenerated > ago(lbperiod)\n| where EventType == 'message'\n| where NetworkDirection == 'outbound'\n| where SrcUserUpn != ''\n| where array_length(todynamic(DstUserUpn)) == 1\n| summarize recipients = make_set(tostring(todynamic(DstUserUpn)[0])) by SrcUserUpn\n| extend commcol = SrcUserUpn;\nProofpointPOD\n| where TimeGenerated between (ago(lbtime) .. now())\n| where EventType == 'message'\n| where NetworkDirection == 'outbound'\n| extend isProtected = todynamic(MsgParts)[0]['isProtected']\n| extend mimePgp = todynamic(MsgParts)[0]['detectedMime']\n| where isProtected == 'true' or mimePgp == 'application/pgp-encrypted'\n| extend DstUserMail = tostring(todynamic(DstUserUpn)[0])\n| extend commcol = tostring(todynamic(DstUserUpn)[0])\n| join knownrecipients on commcol\n| where recipients !contains DstUserMail\n| project SrcUserUpn, DstUserMail\n| extend AccountCustomEntity = SrcUserUpn\n",
        "queryFrequency": "PT30M",
        "queryPeriod": "PT30M",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Exfiltration"
        ],
        "techniques": [
          "T1567"
        ],
        "templateVersion": "1.1.1",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}