Detect DNS queries reporting multiple errors from different clients - Static threshold based ASIM DNS Solution

let lookback=1h;
let threshold = 2;
let errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']); 
_Im_Dns(starttime=ago(lookback)) 
  | where EventResultDetails has_any (errors) 
  | summarize SrcIPs = make_set(SrcIpAddr, 100), Dvcs = make_set(Dvc, 100), ResourceIds = make_set(_ResourceId, 100) by DnsQuery, bin(TimeGenerated, 10min) 
  | where array_length(SrcIPs) >= threshold 
  | extend TotalIPs = array_length(SrcIPs),IPCountthreshold = threshold 
  | extend DomainName = strcat(split(DnsQuery, ".")[1], ".", split(DnsQuery, ".")[2])  
  | mv-expand SrcIPs  
  | extend SrcIP = tostring(SrcIPs)  
  | mv-expand Dvcs  
  | extend Dvc = tostring(Dvcs)  
  | mv-expand ResourceIds  
  | extend ResourceId = tostring(ResourceIds)  
  | extend Dvc = strcat(split(Dvc, ".")[0])
  | summarize Start=min(TimeGenerated), End=max(TimeGenerated) by SrcIP, Dvc, ResourceId, DnsQuery, DomainName
  | extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)

customDetails:
  IPCountthreshold: IPCountthreshold
  TotalIPs: TotalIPs
  SrcIPs: SrcIPs
triggerOperator: gt
queryFrequency: 1h
description: |
    'This rule creates an alert when multiple clients report errors for the same DNS query. This helps in identifying possible similar C2 communications originating from different clients. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
alertDetailsOverride:
  alertDescriptionFormat: |-
    Multiple errors were detected on different clients for the same DNS query. These unsuccessful responses can be an indication of C2 communication. 

    Threshold for total clients reporting errors: '{{IPCountthreshold}}'

    Current count of clients reporting errors for this DNS query: '{{TotalIPs}}'

    Clients requesting this DNSQuery include:

    '{{SrcIPs}}'    
  alertDisplayNameFormat: "[Static threshold] Multiple errors for the same DNS query has been detected - '{{DnsQuery}}'"
status: Available
kind: Scheduled
triggerThreshold: 0
requiredDataConnectors: []
version: 1.0.3
eventGroupingSettings:
  aggregationKind: SingleAlert
queryPeriod: 1h
name: Detect DNS queries reporting multiple errors from different clients - Static threshold based (ASIM DNS Solution)
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/MultipleErrorsReportedForSameDNSQueryStaticThresholdBased.yaml
id: 5b8344eb-fa28-4ac3-bcff-bc19d5d63089
tags:
- Schema: ASimDns
  SchemaVersion: 0.1.6
tactics:
- CommandAndControl
relevantTechniques:
- T1568
- T1573
- T1008
severity: Medium
entityMappings:
- fieldMappings:
  - identifier: DomainName
    columnName: DnsQuery
  entityType: DNS
- fieldMappings:
  - identifier: Address
    columnName: SrcIP
  entityType: IP
- fieldMappings:
  - identifier: ResourceId
    columnName: ResourceId
  entityType: AzureResource
- fieldMappings:
  - identifier: Url
    columnName: DnsQuery
  entityType: Url
- fieldMappings:
  - identifier: HostName
    columnName: HostName
  - identifier: NTDomain
    columnName: HostNameDomain
  entityType: Host
query: |
  let lookback=1h;
  let threshold = 2;
  let errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']); 
  _Im_Dns(starttime=ago(lookback)) 
    | where EventResultDetails has_any (errors) 
    | summarize SrcIPs = make_set(SrcIpAddr, 100), Dvcs = make_set(Dvc, 100), ResourceIds = make_set(_ResourceId, 100) by DnsQuery, bin(TimeGenerated, 10min) 
    | where array_length(SrcIPs) >= threshold 
    | extend TotalIPs = array_length(SrcIPs),IPCountthreshold = threshold 
    | extend DomainName = strcat(split(DnsQuery, ".")[1], ".", split(DnsQuery, ".")[2])  
    | mv-expand SrcIPs  
    | extend SrcIP = tostring(SrcIPs)  
    | mv-expand Dvcs  
    | extend Dvc = tostring(Dvcs)  
    | mv-expand ResourceIds  
    | extend ResourceId = tostring(ResourceIds)  
    | extend Dvc = strcat(split(Dvc, ".")[0])
    | summarize Start=min(TimeGenerated), End=max(TimeGenerated) by SrcIP, Dvc, ResourceId, DnsQuery, DomainName
    | extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
    | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)  

{
  "$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/5b8344eb-fa28-4ac3-bcff-bc19d5d63089')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/5b8344eb-fa28-4ac3-bcff-bc19d5d63089')]",
      "properties": {
        "alertDetailsOverride": {
          "alertDescriptionFormat": "Multiple errors were detected on different clients for the same DNS query. These unsuccessful responses can be an indication of C2 communication. \n\nThreshold for total clients reporting errors: '{{IPCountthreshold}}'\n\nCurrent count of clients reporting errors for this DNS query: '{{TotalIPs}}'\n\nClients requesting this DNSQuery include:\n\n'{{SrcIPs}}'",
          "alertDisplayNameFormat": "[Static threshold] Multiple errors for the same DNS query has been detected - '{{DnsQuery}}'"
        },
        "alertRuleTemplateName": "5b8344eb-fa28-4ac3-bcff-bc19d5d63089",
        "customDetails": {
          "IPCountthreshold": "IPCountthreshold",
          "SrcIPs": "SrcIPs",
          "TotalIPs": "TotalIPs"
        },
        "description": "'This rule creates an alert when multiple clients report errors for the same DNS query. This helps in identifying possible similar C2 communications originating from different clients. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'\n",
        "displayName": "Detect DNS queries reporting multiple errors from different clients - Static threshold based (ASIM DNS Solution)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "DNS",
            "fieldMappings": [
              {
                "columnName": "DnsQuery",
                "identifier": "DomainName"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SrcIP",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "AzureResource",
            "fieldMappings": [
              {
                "columnName": "ResourceId",
                "identifier": "ResourceId"
              }
            ]
          },
          {
            "entityType": "Url",
            "fieldMappings": [
              {
                "columnName": "DnsQuery",
                "identifier": "Url"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "HostNameDomain",
                "identifier": "NTDomain"
              }
            ]
          }
        ],
        "eventGroupingSettings": {
          "aggregationKind": "SingleAlert"
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/MultipleErrorsReportedForSameDNSQueryStaticThresholdBased.yaml",
        "query": "let lookback=1h;\nlet threshold = 2;\nlet errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']); \n_Im_Dns(starttime=ago(lookback)) \n  | where EventResultDetails has_any (errors) \n  | summarize SrcIPs = make_set(SrcIpAddr, 100), Dvcs = make_set(Dvc, 100), ResourceIds = make_set(_ResourceId, 100) by DnsQuery, bin(TimeGenerated, 10min) \n  | where array_length(SrcIPs) >= threshold \n  | extend TotalIPs = array_length(SrcIPs),IPCountthreshold = threshold \n  | extend DomainName = strcat(split(DnsQuery, \".\")[1], \".\", split(DnsQuery, \".\")[2])  \n  | mv-expand SrcIPs  \n  | extend SrcIP = tostring(SrcIPs)  \n  | mv-expand Dvcs  \n  | extend Dvc = tostring(Dvcs)  \n  | mv-expand ResourceIds  \n  | extend ResourceId = tostring(ResourceIds)  \n  | extend Dvc = strcat(split(Dvc, \".\")[0])\n  | summarize Start=min(TimeGenerated), End=max(TimeGenerated) by SrcIP, Dvc, ResourceId, DnsQuery, DomainName\n  | extend HostName = tostring(split(Dvc, \".\")[0]), DomainIndex = toint(indexof(Dvc, '.'))\n  | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl"
        ],
        "tags": [
          {
            "Schema": "ASimDns",
            "SchemaVersion": "0.1.6"
          }
        ],
        "techniques": [
          "T1008",
          "T1568",
          "T1573"
        ],
        "templateVersion": "1.0.3",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}