Tailscale Tailnet lock validation failed

Tailscale_Devices_CL
| where TimeGenerated > ago(1h)
| summarize arg_max(TimeGenerated, *) by DeviceId
| where isnotempty(TailnetLockError)
| project TimeGenerated, DeviceName, Hostname, User, Os, ClientVersion, TailnetLockError, TailnetLockKey, LastSeen, Authorized

entityMappings:
- entityType: Host
  fieldMappings:
  - identifier: HostName
    columnName: Hostname
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: User
name: 'Tailscale: Tailnet lock validation failed'
query: |
  Tailscale_Devices_CL
  | where TimeGenerated > ago(1h)
  | summarize arg_max(TimeGenerated, *) by DeviceId
  | where isnotempty(TailnetLockError)
  | project TimeGenerated, DeviceName, Hostname, User, Os, ClientVersion, TailnetLockError, TailnetLockKey, LastSeen, Authorized
kind: Scheduled
triggerOperator: gt
status: Available
queryPeriod: 1h
requiredDataConnectors:
- connectorId: TailscaleCCF
  dataTypes:
  - Tailscale_Devices_CL
tactics:
- DefenseEvasion
- InitialAccess
description-detailed: |
  Identifies tailnet devices with a non-empty TailnetLockError, indicating the device failed tailnet-lock cryptographic validation. Tailnet lock requires new node-keys be co-signed by trusted signers; errors here are the only direct signal of a node-key injection attempt.
description: Identifies tailnet devices with a non-empty TailnetLockError, indicating the device failed tailnet-lock cryptographic validation. Suspicious - likely an unsigned node attempting to join.
severity: High
incidentConfiguration:
  groupingConfiguration:
    lookbackDuration: P1D
    enabled: true
    reopenClosedIncident: false
    matchingMethod: AllEntities
  createIncident: true
id: e9f0a1b2-3456-7890-12cd-ef1234560040
triggerThreshold: 0
queryFrequency: 1h
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Tailscale%20%28CCF%29/Analytic%20Rules/TailscaleTailnetLockValidationFailed.yaml
version: 1.0.0
relevantTechniques:
- T1556
- T1078

{
  "$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/e9f0a1b2-3456-7890-12cd-ef1234560040')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/e9f0a1b2-3456-7890-12cd-ef1234560040')]",
      "properties": {
        "alertRuleTemplateName": "e9f0a1b2-3456-7890-12cd-ef1234560040",
        "customDetails": null,
        "description": "Identifies tailnet devices with a non-empty TailnetLockError, indicating the device failed tailnet-lock cryptographic validation. Suspicious - likely an unsigned node attempting to join.",
        "description-detailed": "Identifies tailnet devices with a non-empty TailnetLockError, indicating the device failed tailnet-lock cryptographic validation. Tailnet lock requires new node-keys be co-signed by trusted signers; errors here are the only direct signal of a node-key injection attempt.\n",
        "displayName": "Tailscale: Tailnet lock validation failed",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "Hostname",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "User",
                "identifier": "FullName"
              }
            ]
          }
        ],
        "incidentConfiguration": {
          "createIncident": true,
          "groupingConfiguration": {
            "enabled": true,
            "lookbackDuration": "P1D",
            "matchingMethod": "AllEntities",
            "reopenClosedIncident": false
          }
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Tailscale%20%28CCF%29/Analytic%20Rules/TailscaleTailnetLockValidationFailed.yaml",
        "query": "Tailscale_Devices_CL\n| where TimeGenerated > ago(1h)\n| summarize arg_max(TimeGenerated, *) by DeviceId\n| where isnotempty(TailnetLockError)\n| project TimeGenerated, DeviceName, Hostname, User, Os, ClientVersion, TailnetLockError, TailnetLockKey, LastSeen, Authorized\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "High",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion",
          "InitialAccess"
        ],
        "techniques": [
          "T1078",
          "T1556"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}