Detect excessive NXDOMAIN DNS queries - Anomaly based ASIM DNS Solution

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Id	02f23312-1a33-4390-8b80-f7cd4df4dea0
Rulename	Detect excessive NXDOMAIN DNS queries - Anomaly based (ASIM DNS Solution)
Description	This rule makes use of the series decompose anomaly method to generate an alert when client requests excessive amount of DNS queries to non-existent domains. This helps in identifying possible C2 communications. It utilizes ASIM normalization and is applied to any source that supports the ASIM DNS schema.
Severity	Medium
Tactics	CommandAndControl
Techniques	T1568 T1008
Kind	Scheduled
Query frequency	1d
Query period	14d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/ExcessiveNXDOMAINDNSQueriesAnomalyBased.yaml
Version	1.0.2
Arm template	02f23312-1a33-4390-8b80-f7cd4df4dea0.json

KQL

let threshold = 2.5;
let min_t = ago(14d);
let max_t = now();
let dt = 1d;
let summarizationexist = (
  union isfuzzy=true 
      (
      DNS_Summarized_Logs_ip_CL
      | where EventTime_t > ago(1d) 
      | project v = int(2)
      ),
      (
      print int(1) 
      | project v = print_0
      )
  | summarize maxv = max(v)
  | extend sumexist = (maxv > 1)
  );
let allData = union isfuzzy=true
      (
      (datatable(exists: int, sumexist: bool)[1, false]
      | join (summarizationexist) on sumexist)
      | join (
          _Im_Dns(responsecodename='NXDOMAIN', starttime=todatetime(min_t), endtime=max_t)
          | summarize Count=count() by SrcIpAddr, bin(TimeGenerated, 1h)
          | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)
          )
          on exists
      | project-away exists, maxv, sum*
      ),
      (
      DNS_Summarized_Logs_ip_CL
      | where EventTime_t > min_t and EventResultDetails_s == 'NXDOMAIN'
      | summarize Count=toint(sum(count__d)) by SrcIpAddr=SrcIpAddr_s, bin(EventTime=EventTime_t, 1h)
      );
allData
| make-series EventCount=sum(Count) on EventTime from min_t to max_t step dt by SrcIpAddr
| extend (anomalies, score, baseline) = series_decompose_anomalies(EventCount, threshold, -1, 'linefit')
| mv-expand anomalies, score, baseline, EventTime, EventCount
| extend
  anomalies = toint(anomalies),
  score = toint(score),
  baseline = toint(baseline),
  EventTime = todatetime(EventTime),
  Total = tolong(EventCount)
| where EventTime >= ago(dt)
| where score >= threshold * 2
| join kind=inner(_Im_Dns(responsecodename='NXDOMAIN', starttime=ago(dt), endtime=max_t)
  | summarize DNSQueries = make_set(DnsQuery) by SrcIpAddr)
  on SrcIpAddr
| project-away SrcIpAddr1

YAML

relevantTechniques:
- T1568
- T1008
name: Detect excessive NXDOMAIN DNS queries - Anomaly based (ASIM DNS Solution)
requiredDataConnectors: []
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
  entityType: IP
triggerThreshold: 0
id: 02f23312-1a33-4390-8b80-f7cd4df4dea0
tactics:
- CommandAndControl
version: 1.0.2
customDetails:
  baseline: baseline
  DNSQueries: DNSQueries
  Total: Total
  AnomalyScore: score
queryPeriod: 14d
alertDetailsOverride:
  alertDisplayNameFormat: "[Anomaly] Excessive NXDOMAIN DNS Queries has been detected from client IP: '{{SrcIpAddr}}'"
  alertDescriptionFormat: |-
    This client is generating excessive amount of DNS queries for non-existent domains. This can be an indication of possible C2 communications.

    Baseline for 'NXDOMAIN' error count for this client: '{{baseline}}'

    Current 'NXDOMAIN' error count for this client: '{{Total}}'

    DNS queries requested by the client include:

    '{{DNSQueries}}'    
triggerOperator: gt
kind: Scheduled
tags:
- Schema: ASimDns
  SchemaVersion: 0.1.6
eventGroupingSettings:
  aggregationKind: AlertPerResult
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/ExcessiveNXDOMAINDNSQueriesAnomalyBased.yaml
queryFrequency: 1d
severity: Medium
status: Available
description: |
    'This rule makes use of the series decompose anomaly method to generate an alert when client requests excessive amount of DNS queries to non-existent domains. This helps in identifying possible C2 communications. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
query: |
  let threshold = 2.5;
  let min_t = ago(14d);
  let max_t = now();
  let dt = 1d;
  let summarizationexist = (
    union isfuzzy=true 
        (
        DNS_Summarized_Logs_ip_CL
        | where EventTime_t > ago(1d) 
        | project v = int(2)
        ),
        (
        print int(1) 
        | project v = print_0
        )
    | summarize maxv = max(v)
    | extend sumexist = (maxv > 1)
    );
  let allData = union isfuzzy=true
        (
        (datatable(exists: int, sumexist: bool)[1, false]
        | join (summarizationexist) on sumexist)
        | join (
            _Im_Dns(responsecodename='NXDOMAIN', starttime=todatetime(min_t), endtime=max_t)
            | summarize Count=count() by SrcIpAddr, bin(TimeGenerated, 1h)
            | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)
            )
            on exists
        | project-away exists, maxv, sum*
        ),
        (
        DNS_Summarized_Logs_ip_CL
        | where EventTime_t > min_t and EventResultDetails_s == 'NXDOMAIN'
        | summarize Count=toint(sum(count__d)) by SrcIpAddr=SrcIpAddr_s, bin(EventTime=EventTime_t, 1h)
        );
  allData
  | make-series EventCount=sum(Count) on EventTime from min_t to max_t step dt by SrcIpAddr
  | extend (anomalies, score, baseline) = series_decompose_anomalies(EventCount, threshold, -1, 'linefit')
  | mv-expand anomalies, score, baseline, EventTime, EventCount
  | extend
    anomalies = toint(anomalies),
    score = toint(score),
    baseline = toint(baseline),
    EventTime = todatetime(EventTime),
    Total = tolong(EventCount)
  | where EventTime >= ago(dt)
  | where score >= threshold * 2
  | join kind=inner(_Im_Dns(responsecodename='NXDOMAIN', starttime=ago(dt), endtime=max_t)
    | summarize DNSQueries = make_set(DnsQuery) by SrcIpAddr)
    on SrcIpAddr
  | project-away SrcIpAddr1

ARM

{
  "$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/02f23312-1a33-4390-8b80-f7cd4df4dea0')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/02f23312-1a33-4390-8b80-f7cd4df4dea0')]",
      "properties": {
        "alertDetailsOverride": {
          "alertDescriptionFormat": "This client is generating excessive amount of DNS queries for non-existent domains. This can be an indication of possible C2 communications.\n\nBaseline for 'NXDOMAIN' error count for this client: '{{baseline}}'\n\nCurrent 'NXDOMAIN' error count for this client: '{{Total}}'\n\nDNS queries requested by the client include:\n\n'{{DNSQueries}}'",
          "alertDisplayNameFormat": "[Anomaly] Excessive NXDOMAIN DNS Queries has been detected from client IP: '{{SrcIpAddr}}'"
        },
        "alertRuleTemplateName": "02f23312-1a33-4390-8b80-f7cd4df4dea0",
        "customDetails": {
          "AnomalyScore": "score",
          "baseline": "baseline",
          "DNSQueries": "DNSQueries",
          "Total": "Total"
        },
        "description": "'This rule makes use of the series decompose anomaly method to generate an alert when client requests excessive amount of DNS queries to non-existent domains. This helps in identifying possible C2 communications. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'\n",
        "displayName": "Detect excessive NXDOMAIN DNS queries - Anomaly based (ASIM DNS Solution)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SrcIpAddr",
                "identifier": "Address"
              }
            ]
          }
        ],
        "eventGroupingSettings": {
          "aggregationKind": "AlertPerResult"
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/ExcessiveNXDOMAINDNSQueriesAnomalyBased.yaml",
        "query": "let threshold = 2.5;\nlet min_t = ago(14d);\nlet max_t = now();\nlet dt = 1d;\nlet summarizationexist = (\n  union isfuzzy=true \n      (\n      DNS_Summarized_Logs_ip_CL\n      | where EventTime_t > ago(1d) \n      | project v = int(2)\n      ),\n      (\n      print int(1) \n      | project v = print_0\n      )\n  | summarize maxv = max(v)\n  | extend sumexist = (maxv > 1)\n  );\nlet allData = union isfuzzy=true\n      (\n      (datatable(exists: int, sumexist: bool)[1, false]\n      | join (summarizationexist) on sumexist)\n      | join (\n          _Im_Dns(responsecodename='NXDOMAIN', starttime=todatetime(min_t), endtime=max_t)\n          | summarize Count=count() by SrcIpAddr, bin(TimeGenerated, 1h)\n          | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)\n          )\n          on exists\n      | project-away exists, maxv, sum*\n      ),\n      (\n      DNS_Summarized_Logs_ip_CL\n      | where EventTime_t > min_t and EventResultDetails_s == 'NXDOMAIN'\n      | summarize Count=toint(sum(count__d)) by SrcIpAddr=SrcIpAddr_s, bin(EventTime=EventTime_t, 1h)\n      );\nallData\n| make-series EventCount=sum(Count) on EventTime from min_t to max_t step dt by SrcIpAddr\n| extend (anomalies, score, baseline) = series_decompose_anomalies(EventCount, threshold, -1, 'linefit')\n| mv-expand anomalies, score, baseline, EventTime, EventCount\n| extend\n  anomalies = toint(anomalies),\n  score = toint(score),\n  baseline = toint(baseline),\n  EventTime = todatetime(EventTime),\n  Total = tolong(EventCount)\n| where EventTime >= ago(dt)\n| where score >= threshold * 2\n| join kind=inner(_Im_Dns(responsecodename='NXDOMAIN', starttime=ago(dt), endtime=max_t)\n  | summarize DNSQueries = make_set(DnsQuery) by SrcIpAddr)\n  on SrcIpAddr\n| project-away SrcIpAddr1\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P14D",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl"
        ],
        "tags": [
          {
            "Schema": "ASimDns",
            "SchemaVersion": "0.1.6"
          }
        ],
        "techniques": [
          "T1008",
          "T1568"
        ],
        "templateVersion": "1.0.2",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}