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. \n\nIt utilizes ASIM normalization and is applied to any source that supports the ASIM DNS schema.
Severity	Medium
Tactics	CommandAndControl
Techniques	T1568 T1008
Required data connectors	AIVectraStream ASimDnsActivityLogs AzureFirewall CiscoUmbrellaDataConnector Corelight DNS GCPDNSDataConnector InfobloxNIOS ISCBind NXLogDnsLogs WindowsForwardedEvents Zscaler
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	1.0.0
Arm template	02f23312-1a33-4390-8b80-f7cd4df4dea0.json

KQL

let threshold = materialize (_GetWatchlist('DNS_Solution_Monitoring_Configuration')
  | where wl_RuleName == 'Anomaly - Excessive NXDOMAIN DNS Queries'
      and wl_Type == 'Detection'
  | project todouble(wl_AnomalyThreshold));
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, toscalar(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 >= (toscalar(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

queryFrequency: 1d
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
tactics:
- CommandAndControl
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. \n\nIt utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
eventGroupingSettings:
  aggregationKind: AlertPerResult
status: Available
relevantTechniques:
- T1568
- T1008
name: Detect excessive NXDOMAIN DNS queries - Anomaly based (ASIM DNS Solution)
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/ExcessiveNXDOMAINDNSQueriesAnomalyBased.yaml
severity: Medium
triggerThreshold: 0
version: 1.0.0
entityMappings:
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
tags:
- Schema: ASimDns
  SchemaVersion: 0.1.6
customDetails:
  baseline: baseline
  DNSQueries: DNSQueries
  AnomalyScore: score
  Total: Total
id: 02f23312-1a33-4390-8b80-f7cd4df4dea0
requiredDataConnectors:
- connectorId: ASimDnsActivityLogs
  dataTypes:
  - ASimDnsActivityLogs
- connectorId: GCPDNSDataConnector
  dataTypes:
  - GCP_DNS_CL
- connectorId: AzureFirewall
  dataTypes:
  - AzureDiagnostics
- connectorId: CiscoUmbrellaDataConnector
  dataTypes:
  - Cisco_Umbrella_proxy_CL
- connectorId: Corelight
  dataTypes:
  - Corelight_CL
- connectorId: InfobloxNIOS
  dataTypes:
  - Syslog
- connectorId: NXLogDnsLogs
  dataTypes:
  - NXLog_DNS_Server_CL
- connectorId: DNS
  dataTypes:
  - DnsEvents
- connectorId: AIVectraStream
  dataTypes:
  - VectraStream_CL
- connectorId: WindowsForwardedEvents
  dataTypes:
  - WindowsEvents
- connectorId: Zscaler
  dataTypes:
  - CommonSecurityLog
- connectorId: ISCBind
  dataTypes:
  - Syslog
kind: Scheduled
query: |
  let threshold = materialize (_GetWatchlist('DNS_Solution_Monitoring_Configuration')
    | where wl_RuleName == 'Anomaly - Excessive NXDOMAIN DNS Queries'
        and wl_Type == 'Detection'
    | project todouble(wl_AnomalyThreshold));
  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, toscalar(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 >= (toscalar(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  
queryPeriod: 14d

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/02f23312-1a33-4390-8b80-f7cd4df4dea0')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/02f23312-1a33-4390-8b80-f7cd4df4dea0')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01",
      "properties": {
        "displayName": "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. \\n\\nIt utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "let threshold = materialize (_GetWatchlist('DNS_Solution_Monitoring_Configuration')\n  | where wl_RuleName == 'Anomaly - Excessive NXDOMAIN DNS Queries'\n      and wl_Type == 'Detection'\n  | project todouble(wl_AnomalyThreshold));\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, toscalar(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 >= (toscalar(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",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl"
        ],
        "techniques": [
          "T1568",
          "T1008"
        ],
        "alertRuleTemplateName": "02f23312-1a33-4390-8b80-f7cd4df4dea0",
        "eventGroupingSettings": {
          "aggregationKind": "AlertPerResult"
        },
        "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.\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}}'"
        },
        "customDetails": {
          "baseline": "baseline",
          "DNSQueries": "DNSQueries",
          "AnomalyScore": "score",
          "Total": "Total"
        },
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "identifier": "Address",
                "columnName": "SrcIpAddr"
              }
            ]
          }
        ],
        "status": "Available",
        "templateVersion": "1.0.0",
        "tags": [
          {
            "Schema": "ASimDns",
            "SchemaVersion": "0.1.6"
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/ExcessiveNXDOMAINDNSQueriesAnomalyBased.yaml"
      }
    }
  ]
}