VMware ESXi - Multiple new VMs started

let threshold = 5;
let a_vm = 
VMwareESXi
| where SyslogMessage has ('VmPoweredOnEvent')
| extend DstHostname = extract(@'\[\d+\]\s+\[(.*?)\s+on', 1, SyslogMessage)
| summarize vm_l = make_set(DstHostname,200)
| extend k=1;
VMwareESXi
| where SyslogMessage has ('VmPoweredOnEvent')
| extend DstHostname = extract(@'\[\d+\]\s+\[(.*?)\s+on', 1, SyslogMessage)
| extend SrcUsername = extract(@'\[info\]\s+\[(.*?)\]', 1, SyslogMessage)
| extend k = 1
| join (a_vm) on k
| where vm_l !has DstHostname
| summarize n_vm = make_set(DstHostname,200) by SrcUsername, bin(TimeGenerated, 10m)
| where array_length(n_vm) >= threshold
| extend hostname = iff(array_length(n_vm) > 0, n_vm[0], "")
| extend NTDomain = tostring(split(hostname, '\\', 1)[0]), HostName = tostring(split(hostname, '.', 0)[0])

severity: Medium
queryFrequency: 1h
relevantTechniques:
- T1078
tactics:
- InitialAccess
kind: Scheduled
query: |
  let threshold = 5;
  let a_vm = 
  VMwareESXi
  | where SyslogMessage has ('VmPoweredOnEvent')
  | extend DstHostname = extract(@'\[\d+\]\s+\[(.*?)\s+on', 1, SyslogMessage)
  | summarize vm_l = make_set(DstHostname,200)
  | extend k=1;
  VMwareESXi
  | where SyslogMessage has ('VmPoweredOnEvent')
  | extend DstHostname = extract(@'\[\d+\]\s+\[(.*?)\s+on', 1, SyslogMessage)
  | extend SrcUsername = extract(@'\[info\]\s+\[(.*?)\]', 1, SyslogMessage)
  | extend k = 1
  | join (a_vm) on k
  | where vm_l !has DstHostname
  | summarize n_vm = make_set(DstHostname,200) by SrcUsername, bin(TimeGenerated, 10m)
  | where array_length(n_vm) >= threshold
  | extend hostname = iff(array_length(n_vm) > 0, n_vm[0], "")
  | extend NTDomain = tostring(split(hostname, '\\', 1)[0]), HostName = tostring(split(hostname, '.', 0)[0])  
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/VMWareESXi/Analytic Rules/ESXiMultipleNewVM.yaml
queryPeriod: 1h
status: Available
version: 1.0.1
name: VMware ESXi - Multiple new VMs started
requiredDataConnectors:
- dataTypes:
  - VMwareESXi
  connectorId: VMwareESXi
triggerOperator: gt
entityMappings:
- entityType: Host
  fieldMappings:
  - identifier: HostName
    columnName: HostName
  - identifier: NTDomain
    columnName: NTDomain
id: bdea247f-7d17-498c-ac0e-c7e764cbdbbe
description: |
    'Detects when multiple new VMs were started.'
triggerThreshold: 0

{
  "$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/bdea247f-7d17-498c-ac0e-c7e764cbdbbe')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/bdea247f-7d17-498c-ac0e-c7e764cbdbbe')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01-preview",
      "properties": {
        "displayName": "VMware ESXi - Multiple new VMs started",
        "description": "'Detects when multiple new VMs were started.'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "let threshold = 5;\nlet a_vm = \nVMwareESXi\n| where SyslogMessage has ('VmPoweredOnEvent')\n| extend DstHostname = extract(@'\\[\\d+\\]\\s+\\[(.*?)\\s+on', 1, SyslogMessage)\n| summarize vm_l = make_set(DstHostname,200)\n| extend k=1;\nVMwareESXi\n| where SyslogMessage has ('VmPoweredOnEvent')\n| extend DstHostname = extract(@'\\[\\d+\\]\\s+\\[(.*?)\\s+on', 1, SyslogMessage)\n| extend SrcUsername = extract(@'\\[info\\]\\s+\\[(.*?)\\]', 1, SyslogMessage)\n| extend k = 1\n| join (a_vm) on k\n| where vm_l !has DstHostname\n| summarize n_vm = make_set(DstHostname,200) by SrcUsername, bin(TimeGenerated, 10m)\n| where array_length(n_vm) >= threshold\n| extend hostname = iff(array_length(n_vm) > 0, n_vm[0], \"\")\n| extend NTDomain = tostring(split(hostname, '\\\\', 1)[0]), HostName = tostring(split(hostname, '.', 0)[0])\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1078"
        ],
        "alertRuleTemplateName": "bdea247f-7d17-498c-ac0e-c7e764cbdbbe",
        "customDetails": null,
        "entityMappings": [
          {
            "fieldMappings": [
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "NTDomain",
                "identifier": "NTDomain"
              }
            ],
            "entityType": "Host"
          }
        ],
        "templateVersion": "1.0.1",
        "status": "Available",
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/VMWareESXi/Analytic Rules/ESXiMultipleNewVM.yaml"
      }
    }
  ]
}