Tailscale Premium Mass fan-out from single node

let dstThreshold = 25;
Tailscale_Network_CL
| where TimeGenerated > ago(15m)
| where HasVirtualTraffic
| mv-expand t = VirtualTraffic
| extend Src = tostring(t.src), Dst = tostring(t.dst)
| summarize UniqueDestinations = dcount(Dst), TopDestinations = make_set(Dst, 25) by NodeId, SrcNodeName, SrcUser, SrcOs, SrcTags=tostring(SrcTags), Src
| where UniqueDestinations >= dstThreshold
| order by UniqueDestinations desc

severity: High
relevantTechniques:
- T1018
- T1021
- T1046
version: 1.0.0
triggerThreshold: 0
tactics:
- Discovery
- LateralMovement
query: |
  let dstThreshold = 25;
  Tailscale_Network_CL
  | where TimeGenerated > ago(15m)
  | where HasVirtualTraffic
  | mv-expand t = VirtualTraffic
  | extend Src = tostring(t.src), Dst = tostring(t.dst)
  | summarize UniqueDestinations = dcount(Dst), TopDestinations = make_set(Dst, 25) by NodeId, SrcNodeName, SrcUser, SrcOs, SrcTags=tostring(SrcTags), Src
  | where UniqueDestinations >= dstThreshold
  | order by UniqueDestinations desc
name: 'Tailscale Premium: Mass fan-out from single node'
kind: Scheduled
entityMappings:
- entityType: Host
  fieldMappings:
  - identifier: HostName
    columnName: SrcNodeName
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: SrcUser
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: Src
triggerOperator: gt
requiredDataConnectors:
- dataTypes:
  - Tailscale_Network_CL
  connectorId: TailscalePremiumCCF
incidentConfiguration:
  groupingConfiguration:
    matchingMethod: AllEntities
    lookbackDuration: PT5H
    enabled: true
    reopenClosedIncident: false
  createIncident: true
queryFrequency: 15m
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Tailscale%20%28CCF%29/Analytic%20Rules/TailscalePremiumMassFanOut.yaml
status: Available
queryPeriod: 15m
id: f4a5b6c7-4d5e-6f7a-8b9c-0d1e2f3a4b5c
description: |
  Identifies when a single node initiates flows to 25 or more unique destinations within a 15-minute window. Sudden fan-out is consistent with port scanning, lateral discovery, or worm-style propagation. Requires Tailscale Premium or Enterprise.

{
  "$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/f4a5b6c7-4d5e-6f7a-8b9c-0d1e2f3a4b5c')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/f4a5b6c7-4d5e-6f7a-8b9c-0d1e2f3a4b5c')]",
      "properties": {
        "alertRuleTemplateName": "f4a5b6c7-4d5e-6f7a-8b9c-0d1e2f3a4b5c",
        "customDetails": null,
        "description": "Identifies when a single node initiates flows to 25 or more unique destinations within a 15-minute window. Sudden fan-out is consistent with port scanning, lateral discovery, or worm-style propagation. Requires Tailscale Premium or Enterprise.\n",
        "displayName": "Tailscale Premium: Mass fan-out from single node",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "SrcNodeName",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "SrcUser",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "Src",
                "identifier": "Address"
              }
            ]
          }
        ],
        "incidentConfiguration": {
          "createIncident": true,
          "groupingConfiguration": {
            "enabled": true,
            "lookbackDuration": "PT5H",
            "matchingMethod": "AllEntities",
            "reopenClosedIncident": false
          }
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Tailscale%20%28CCF%29/Analytic%20Rules/TailscalePremiumMassFanOut.yaml",
        "query": "let dstThreshold = 25;\nTailscale_Network_CL\n| where TimeGenerated > ago(15m)\n| where HasVirtualTraffic\n| mv-expand t = VirtualTraffic\n| extend Src = tostring(t.src), Dst = tostring(t.dst)\n| summarize UniqueDestinations = dcount(Dst), TopDestinations = make_set(Dst, 25) by NodeId, SrcNodeName, SrcUser, SrcOs, SrcTags=tostring(SrcTags), Src\n| where UniqueDestinations >= dstThreshold\n| order by UniqueDestinations desc\n",
        "queryFrequency": "PT15M",
        "queryPeriod": "PT15M",
        "severity": "High",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Discovery",
          "LateralMovement"
        ],
        "techniques": [
          "T1018",
          "T1021",
          "T1046"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}