Tailscale Premium Network flow beaconing detected

let lookback = 2d;
let minFlows = 10;
let beaconPercentThreshold = 80.0;
Tailscale_Network_CL
| where TimeGenerated > ago(lookback)
| where HasVirtualTraffic
| mv-expand t = VirtualTraffic
| extend Src = tostring(t.src), Dst = tostring(t.dst), Proto = toint(t.proto)
| project TimeGenerated, Src, Dst, Proto, SrcNodeName, SrcUser, DstNodeName, DstUser
| sort by Src asc, Dst asc, Proto asc, TimeGenerated asc
| serialize
| extend NextTime = next(TimeGenerated), NextSrc = next(Src), NextDst = next(Dst), NextProto = next(Proto)
| where Src == NextSrc and Dst == NextDst and Proto == NextProto
| extend DeltaSec = datetime_diff('second', NextTime, TimeGenerated)
| where DeltaSec > 5
| summarize DeltaCount = count() by Src, Dst, Proto, DeltaSec, SrcNodeName, SrcUser, DstNodeName, DstUser
| summarize (MostFrequentDeltaCount, MostFrequentDeltaSec) = arg_max(DeltaCount, DeltaSec), TotalFlows = sum(DeltaCount) by Src, Dst, Proto, SrcNodeName, SrcUser, DstNodeName, DstUser
| where TotalFlows >= minFlows
| extend BeaconPercent = round(MostFrequentDeltaCount * 100.0 / TotalFlows, 1)
| where BeaconPercent >= beaconPercentThreshold

incidentConfiguration:
  groupingConfiguration:
    lookbackDuration: P1D
    reopenClosedIncident: false
    matchingMethod: AllEntities
    enabled: true
  createIncident: true
name: 'Tailscale Premium: Network flow beaconing detected'
triggerOperator: gt
query: |
  let lookback = 2d;
  let minFlows = 10;
  let beaconPercentThreshold = 80.0;
  Tailscale_Network_CL
  | where TimeGenerated > ago(lookback)
  | where HasVirtualTraffic
  | mv-expand t = VirtualTraffic
  | extend Src = tostring(t.src), Dst = tostring(t.dst), Proto = toint(t.proto)
  | project TimeGenerated, Src, Dst, Proto, SrcNodeName, SrcUser, DstNodeName, DstUser
  | sort by Src asc, Dst asc, Proto asc, TimeGenerated asc
  | serialize
  | extend NextTime = next(TimeGenerated), NextSrc = next(Src), NextDst = next(Dst), NextProto = next(Proto)
  | where Src == NextSrc and Dst == NextDst and Proto == NextProto
  | extend DeltaSec = datetime_diff('second', NextTime, TimeGenerated)
  | where DeltaSec > 5
  | summarize DeltaCount = count() by Src, Dst, Proto, DeltaSec, SrcNodeName, SrcUser, DstNodeName, DstUser
  | summarize (MostFrequentDeltaCount, MostFrequentDeltaSec) = arg_max(DeltaCount, DeltaSec), TotalFlows = sum(DeltaCount) by Src, Dst, Proto, SrcNodeName, SrcUser, DstNodeName, DstUser
  | where TotalFlows >= minFlows
  | extend BeaconPercent = round(MostFrequentDeltaCount * 100.0 / TotalFlows, 1)
  | where BeaconPercent >= beaconPercentThreshold
queryFrequency: 1h
description: |
  Identifies when flows between a src-dst pair recur at a regular interval (80%+ of inter-flow gaps cluster on the same delta over 10+ flows). Signature of C2 beaconing or scheduled exfiltration. Requires Tailscale Premium or Enterprise.
id: e3f4a5b6-3c4d-5e6f-7a8b-9c0d1e2f3a4b
triggerThreshold: 0
queryPeriod: 2d
version: 1.0.0
kind: Scheduled
status: Available
severity: Medium
requiredDataConnectors:
- connectorId: TailscalePremiumCCF
  dataTypes:
  - Tailscale_Network_CL
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Tailscale%20%28CCF%29/Analytic%20Rules/TailscalePremiumBeaconingDetected.yaml
relevantTechniques:
- T1071
- T1095
- T1029
tactics:
- CommandAndControl
- Exfiltration
entityMappings:
- fieldMappings:
  - identifier: HostName
    columnName: SrcNodeName
  entityType: Host
- fieldMappings:
  - identifier: HostName
    columnName: DstNodeName
  entityType: Host
- fieldMappings:
  - identifier: FullName
    columnName: SrcUser
  entityType: Account
- fieldMappings:
  - identifier: Address
    columnName: Src
  entityType: IP

{
  "$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/e3f4a5b6-3c4d-5e6f-7a8b-9c0d1e2f3a4b')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/e3f4a5b6-3c4d-5e6f-7a8b-9c0d1e2f3a4b')]",
      "properties": {
        "alertRuleTemplateName": "e3f4a5b6-3c4d-5e6f-7a8b-9c0d1e2f3a4b",
        "customDetails": null,
        "description": "Identifies when flows between a src-dst pair recur at a regular interval (80%+ of inter-flow gaps cluster on the same delta over 10+ flows). Signature of C2 beaconing or scheduled exfiltration. Requires Tailscale Premium or Enterprise.\n",
        "displayName": "Tailscale Premium: Network flow beaconing detected",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "SrcNodeName",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "DstNodeName",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "SrcUser",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "Src",
                "identifier": "Address"
              }
            ]
          }
        ],
        "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/TailscalePremiumBeaconingDetected.yaml",
        "query": "let lookback = 2d;\nlet minFlows = 10;\nlet beaconPercentThreshold = 80.0;\nTailscale_Network_CL\n| where TimeGenerated > ago(lookback)\n| where HasVirtualTraffic\n| mv-expand t = VirtualTraffic\n| extend Src = tostring(t.src), Dst = tostring(t.dst), Proto = toint(t.proto)\n| project TimeGenerated, Src, Dst, Proto, SrcNodeName, SrcUser, DstNodeName, DstUser\n| sort by Src asc, Dst asc, Proto asc, TimeGenerated asc\n| serialize\n| extend NextTime = next(TimeGenerated), NextSrc = next(Src), NextDst = next(Dst), NextProto = next(Proto)\n| where Src == NextSrc and Dst == NextDst and Proto == NextProto\n| extend DeltaSec = datetime_diff('second', NextTime, TimeGenerated)\n| where DeltaSec > 5\n| summarize DeltaCount = count() by Src, Dst, Proto, DeltaSec, SrcNodeName, SrcUser, DstNodeName, DstUser\n| summarize (MostFrequentDeltaCount, MostFrequentDeltaSec) = arg_max(DeltaCount, DeltaSec), TotalFlows = sum(DeltaCount) by Src, Dst, Proto, SrcNodeName, SrcUser, DstNodeName, DstUser\n| where TotalFlows >= minFlows\n| extend BeaconPercent = round(MostFrequentDeltaCount * 100.0 / TotalFlows, 1)\n| where BeaconPercent >= beaconPercentThreshold\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "P2D",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl",
          "Exfiltration"
        ],
        "techniques": [
          "T1029",
          "T1071",
          "T1095"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}