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Potential DGA(Domain Generation Algorithm) detected via Repetitive Failures - Anomaly based (ASIM DNS Solution)

Description

'This rule makes use of the series decompose anomaly method to detect clients with a high NXDomain response count, which could be indicative of a DGA (cycling through possible C2 domains where most C2s are not live). An alert is generated when new IP address DNS activity is identified as an outlier when compared to the baseline, indicating a recurring pattern. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema. The rule also depends on the "**DNSEssentialsCustomParser**" Parser, so please make sure it is installed and configured before you use this Rule.'
Rule type
Scheduled
Version
1.0.3
Declared status
Available
Query frequency
1d
Query period
14d
Trigger
gt 0

Declared MITRE coverage

KQL query

Original query, unchanged.

let threshold = 2.5;
let min_t = ago(14d);
let max_t = now();
let timeframe = 1d;
// 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 
      (
      DNSEssentialsCustomParser
      | where Type in ("DNS_Summarized_Logs_ip_CL", "DNS_Summarized_Logs_ipV1_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 
      (
      DNSEssentialsCustomParser
      | where Type in ("DNS_Summarized_Logs_ip_CL", "DNS_Summarized_Logs_ipV1_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(responsecodename='NXDOMAIN', starttime=todatetime(ago(2d)), endtime=now())
          | where TimeGenerated > maxSummarizedTime
          | 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(responsecodename='NXDOMAIN', starttime=todatetime(ago(3d)), endtime=now())
          | where TimeGenerated > maxSummarizedTime
          | 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(responsecodename='NXDOMAIN', starttime=todatetime(ago(4d)), endtime=now())
          | where TimeGenerated > maxSummarizedTime
          | 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*
      ),
      (
      DNSEssentialsCustomParser
      | where Type in ("DNS_Summarized_Logs_ip_CL", "DNS_Summarized_Logs_ipV1_CL")
      | where EventTime_t > min_t and EventResultDetails_s == 'NXDOMAIN'
      | project-rename
          SrcIpAddr=SrcIpAddr_s,
          DnsQuery=DnsQuery_s,
          Count=count__d,
          EventTime=EventTime_t
      | extend Count = toint(Count)
      );
allData
| make-series QueryCount=dcount(DnsQuery) on EventTime from min_t to max_t step timeframe by SrcIpAddr
// include calculated Anomalies, Score and Baseline
| extend (anomalies, score, baseline) = series_decompose_anomalies(QueryCount, threshold, -1, 'linefit')
| mv-expand anomalies, score, baseline, EventTime, QueryCount
| extend
  anomalies = toint(anomalies),
  score = toint(score),
  baseline = toint(baseline),
  EventTime = todatetime(EventTime),
  Total = tolong(QueryCount)
| where EventTime >= ago(timeframe)
| where score >= threshold * 2
// Join allData to include DnsQuery details
| join kind=inner(allData
  | where TimeGenerated >= ago(timeframe)
  | summarize DNSQueries = make_set(DnsQuery, 1000) by SrcIpAddr)
  on SrcIpAddr
| project-away SrcIpAddr1

Declared entities

IP

Related content

Links established from declared identifiers and solution manifests.

Source provenance

GitHub

Displayed values come from files in Azure/Azure-Sentinel. They describe the published template, not your workspace configuration.

Source identifier
01191239-274e-43c9-b154-3a042692af06
Additional source files 2Solutions/DNS Essentials/Analytic Rules/PotentialDGADetectedviaRepetitiveFailuresAnomalyBased.yamlsource ↗Solutions/DNS Essentials/Data/Solution_DNS.jsonsolution-membership ↗
GSTEP / CATALOG TRACKING

Added to catalog : 16 Sept 2026 · 05:49 UTC
Last change observed : 16 Sept 2026 · 05:49 UTC

GSTEP sync dates, separate from the source content’s publication dates.