Detect DNS queries reporting multiple errors from different clients - Anomaly Based ASIM DNS Solution

let threshold = 2.5;
let min_t = ago(14d);
let max_t = now();
let dt = 1d;
let Errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']);
// calculate avg. eps(events per second)
let eps = materialize (_Im_Dns | project TimeGenerated | where TimeGenerated > ago(5m) | count | extend Count = Count/300);
let maxSummarizedTime = toscalar (
  union isfuzzy=true 
      (
          DNS_Summarized_Logs_ip_CL 
              | where EventTime_t >= min_t
              | summarize max_TimeGenerated=max(EventTime_t)
              | extend max_TimeGenerated = datetime_add('hour',1,max_TimeGenerated)
      ),
      (
          print(min_t)
          | project max_TimeGenerated = print_0
      )
    | summarize maxTimeGenerated = max(max_TimeGenerated) 
  );
  let summarizationexist = materialize(
            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] | where toscalar(eps) > 1000 | join (summarizationexist) on sumexist) | join (
  _Im_Dns(starttime=todatetime(ago(2d)), endtime=now())
  | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)
  | summarize Count=count() by SrcIpAddr, DnsQuery, bin(TimeGenerated,1h)
  | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)
  ) on exists
  | project-away exists, maxv, sum*
),
(
  (datatable(exists:int, sumexist:bool)[1,false] | where toscalar(eps) between (501 .. 1000) | join (summarizationexist) on sumexist) | join (
  _Im_Dns(starttime=todatetime(ago(3d)), endtime=now())
  | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)
  | summarize Count=count() by SrcIpAddr, DnsQuery, bin(TimeGenerated,1h)
  | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)
  ) on exists
  | project-away exists, maxv, sum*
),
(
  (datatable(exists:int, sumexist:bool)[1,false] | where toscalar(eps) <= 500 | join (summarizationexist) on sumexist) | join (
  _Im_Dns(starttime=todatetime(ago(4d)), endtime=now())
  | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)
  | summarize Count=count() by SrcIpAddr, DnsQuery, 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 in (Errors)
      | project-rename SrcIpAddr=SrcIpAddr_s, DnsQuery=DnsQuery_s, Count=count__d, EventTime=EventTime_t
      | extend Count = toint(Count) 
);
allData
| make-series TotalIPCount=dcount(SrcIpAddr) on EventTime from min_t to max_t step dt by DnsQuery
| extend (anomalies, score, baseline) = series_decompose_anomalies(TotalIPCount, threshold, -1, 'linefit')
| mv-expand anomalies, score, baseline, EventTime, TotalIPCount
| extend
  anomalies = toint(anomalies),
  score = toint(score),
  baseline = toint(baseline),
  EventTime = todatetime(EventTime),
  TotalIPs = tolong(TotalIPCount)
| where EventTime >= ago(dt)
| where score >= threshold * 2
| join kind=inner(allData | where TimeGenerated>ago(dt) | summarize SrcIps = make_set(SrcIpAddr,1000) by DnsQuery) on DnsQuery
| project-away DnsQuery1

customDetails:
  SrcIps: SrcIps
  baseline: baseline
  TotalIPs: TotalIPs
  AnomalyScore: score
id: cf687598-5a2c-46f8-81c8-06b15ed489b1
triggerOperator: gt
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/MultipleErrorsReportedForSameDNSQueryAnomalyBased.yaml
requiredDataConnectors: []
description: |
    'This rule makes use of the series decompose anomaly method to generate an alert when multiple clients report errors for the same DNS query. This rule monitors DNS traffic over a period of 14 days to detect possible similar C2 communication originating from different clients. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
severity: Medium
queryPeriod: 14d
kind: Scheduled
tags:
- SchemaVersion: 0.1.6
  Schema: ASimDns
tactics:
- CommandAndControl
eventGroupingSettings:
  aggregationKind: AlertPerResult
queryFrequency: 1d
query: |
  let threshold = 2.5;
  let min_t = ago(14d);
  let max_t = now();
  let dt = 1d;
  let Errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']);
  // calculate avg. eps(events per second)
  let eps = materialize (_Im_Dns | project TimeGenerated | where TimeGenerated > ago(5m) | count | extend Count = Count/300);
  let maxSummarizedTime = toscalar (
    union isfuzzy=true 
        (
            DNS_Summarized_Logs_ip_CL 
                | where EventTime_t >= min_t
                | summarize max_TimeGenerated=max(EventTime_t)
                | extend max_TimeGenerated = datetime_add('hour',1,max_TimeGenerated)
        ),
        (
            print(min_t)
            | project max_TimeGenerated = print_0
        )
      | summarize maxTimeGenerated = max(max_TimeGenerated) 
    );
    let summarizationexist = materialize(
              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] | where toscalar(eps) > 1000 | join (summarizationexist) on sumexist) | join (
    _Im_Dns(starttime=todatetime(ago(2d)), endtime=now())
    | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)
    | summarize Count=count() by SrcIpAddr, DnsQuery, bin(TimeGenerated,1h)
    | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)
    ) on exists
    | project-away exists, maxv, sum*
  ),
  (
    (datatable(exists:int, sumexist:bool)[1,false] | where toscalar(eps) between (501 .. 1000) | join (summarizationexist) on sumexist) | join (
    _Im_Dns(starttime=todatetime(ago(3d)), endtime=now())
    | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)
    | summarize Count=count() by SrcIpAddr, DnsQuery, bin(TimeGenerated,1h)
    | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)
    ) on exists
    | project-away exists, maxv, sum*
  ),
  (
    (datatable(exists:int, sumexist:bool)[1,false] | where toscalar(eps) <= 500 | join (summarizationexist) on sumexist) | join (
    _Im_Dns(starttime=todatetime(ago(4d)), endtime=now())
    | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)
    | summarize Count=count() by SrcIpAddr, DnsQuery, 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 in (Errors)
        | project-rename SrcIpAddr=SrcIpAddr_s, DnsQuery=DnsQuery_s, Count=count__d, EventTime=EventTime_t
        | extend Count = toint(Count) 
  );
  allData
  | make-series TotalIPCount=dcount(SrcIpAddr) on EventTime from min_t to max_t step dt by DnsQuery
  | extend (anomalies, score, baseline) = series_decompose_anomalies(TotalIPCount, threshold, -1, 'linefit')
  | mv-expand anomalies, score, baseline, EventTime, TotalIPCount
  | extend
    anomalies = toint(anomalies),
    score = toint(score),
    baseline = toint(baseline),
    EventTime = todatetime(EventTime),
    TotalIPs = tolong(TotalIPCount)
  | where EventTime >= ago(dt)
  | where score >= threshold * 2
  | join kind=inner(allData | where TimeGenerated>ago(dt) | summarize SrcIps = make_set(SrcIpAddr,1000) by DnsQuery) on DnsQuery
  | project-away DnsQuery1  
alertDetailsOverride:
  alertDisplayNameFormat: "[Anomaly] Multiple errors for the same DNS query has been detected - '{{DnsQuery}}'"
  alertDescriptionFormat: |-
    Multiple errors were detected on different clients for the same DNS query. These unsuccessful responses can be an indication of C2 communication. 

    Baseline for total clients reporting errors for this DNS query: '{{baseline}}'

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

    Clients requesting this DNS query include:
    '{{SrcIps}}'    
version: 1.0.2
triggerThreshold: 0
entityMappings:
- entityType: DNS
  fieldMappings:
  - columnName: DnsQuery
    identifier: DomainName
status: Available
name: Detect DNS queries reporting multiple errors from different clients - Anomaly Based (ASIM DNS Solution)
relevantTechniques:
- T1568
- T1573
- T1008

{
  "$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/cf687598-5a2c-46f8-81c8-06b15ed489b1')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/cf687598-5a2c-46f8-81c8-06b15ed489b1')]",
      "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\nBaseline for total clients reporting errors for this DNS query: '{{baseline}}'\n\nCurrent count of clients reporting errors for this DNS query: '{{TotalIPs}}'\n\nClients requesting this DNS query include:\n'{{SrcIps}}'",
          "alertDisplayNameFormat": "[Anomaly] Multiple errors for the same DNS query has been detected - '{{DnsQuery}}'"
        },
        "alertRuleTemplateName": "cf687598-5a2c-46f8-81c8-06b15ed489b1",
        "customDetails": {
          "AnomalyScore": "score",
          "baseline": "baseline",
          "SrcIps": "SrcIps",
          "TotalIPs": "TotalIPs"
        },
        "description": "'This rule makes use of the series decompose anomaly method to generate an alert when multiple clients report errors for the same DNS query. This rule monitors DNS traffic over a period of 14 days to detect possible similar C2 communication 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 - Anomaly Based (ASIM DNS Solution)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "DNS",
            "fieldMappings": [
              {
                "columnName": "DnsQuery",
                "identifier": "DomainName"
              }
            ]
          }
        ],
        "eventGroupingSettings": {
          "aggregationKind": "AlertPerResult"
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/MultipleErrorsReportedForSameDNSQueryAnomalyBased.yaml",
        "query": "let threshold = 2.5;\nlet min_t = ago(14d);\nlet max_t = now();\nlet dt = 1d;\nlet Errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']);\n// calculate avg. eps(events per second)\nlet eps = materialize (_Im_Dns | project TimeGenerated | where TimeGenerated > ago(5m) | count | extend Count = Count/300);\nlet maxSummarizedTime = toscalar (\n  union isfuzzy=true \n      (\n          DNS_Summarized_Logs_ip_CL \n              | where EventTime_t >= min_t\n              | summarize max_TimeGenerated=max(EventTime_t)\n              | extend max_TimeGenerated = datetime_add('hour',1,max_TimeGenerated)\n      ),\n      (\n          print(min_t)\n          | project max_TimeGenerated = print_0\n      )\n    | summarize maxTimeGenerated = max(max_TimeGenerated) \n  );\n  let summarizationexist = materialize(\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] | where toscalar(eps) > 1000 | join (summarizationexist) on sumexist) | join (\n  _Im_Dns(starttime=todatetime(ago(2d)), endtime=now())\n  | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)\n  | summarize Count=count() by SrcIpAddr, DnsQuery, bin(TimeGenerated,1h)\n  | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)\n  ) on exists\n  | project-away exists, maxv, sum*\n),\n(\n  (datatable(exists:int, sumexist:bool)[1,false] | where toscalar(eps) between (501 .. 1000) | join (summarizationexist) on sumexist) | join (\n  _Im_Dns(starttime=todatetime(ago(3d)), endtime=now())\n  | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)\n  | summarize Count=count() by SrcIpAddr, DnsQuery, bin(TimeGenerated,1h)\n  | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)\n  ) on exists\n  | project-away exists, maxv, sum*\n),\n(\n  (datatable(exists:int, sumexist:bool)[1,false] | where toscalar(eps) <= 500 | join (summarizationexist) on sumexist) | join (\n  _Im_Dns(starttime=todatetime(ago(4d)), endtime=now())\n  | where TimeGenerated > maxSummarizedTime and EventResultDetails in (Errors)\n  | summarize Count=count() by SrcIpAddr, DnsQuery, bin(TimeGenerated,1h)\n  | extend EventTime = TimeGenerated, Count = toint(Count), exists=int(1)\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 in (Errors)\n      | project-rename SrcIpAddr=SrcIpAddr_s, DnsQuery=DnsQuery_s, Count=count__d, EventTime=EventTime_t\n      | extend Count = toint(Count) \n);\nallData\n| make-series TotalIPCount=dcount(SrcIpAddr) on EventTime from min_t to max_t step dt by DnsQuery\n| extend (anomalies, score, baseline) = series_decompose_anomalies(TotalIPCount, threshold, -1, 'linefit')\n| mv-expand anomalies, score, baseline, EventTime, TotalIPCount\n| extend\n  anomalies = toint(anomalies),\n  score = toint(score),\n  baseline = toint(baseline),\n  EventTime = todatetime(EventTime),\n  TotalIPs = tolong(TotalIPCount)\n| where EventTime >= ago(dt)\n| where score >= threshold * 2\n| join kind=inner(allData | where TimeGenerated>ago(dt) | summarize SrcIps = make_set(SrcIpAddr,1000) by DnsQuery) on DnsQuery\n| project-away DnsQuery1\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",
          "T1573"
        ],
        "templateVersion": "1.0.2",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}