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

id: 01191239-274e-43c9-b154-3a042692af06
name: 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.'
severity: Medium
status: Available 
tags:
  - Schema: ASimDns
    SchemaVersion: 0.1.6
requiredDataConnectors: []
queryFrequency: 1d
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1568
  - T1008
query: |
  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 
        (
        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(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*
        ),
        (
        DNS_Summarized_Logs_ip_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
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
eventGroupingSettings:
  aggregationKind: AlertPerResult
customDetails:
  DNSQueries: DNSQueries
  AnomalyScore: score
  baseline: baseline
  Total: Total
alertDetailsOverride:
  alertDisplayNameFormat: "[Anomaly] Potential DGA (Domain Generation Algorithm) originating from client IP: '{{SrcIpAddr}}' has been detected."
  alertDescriptionFormat: "Client has been identified with high NXDomain count which could be indicative of a DGA (cycling through possible C2 domains where most C2s are not live). This client is found to be communicating with multiple Domains which do not exist.\n\nBaseline Domain or DNS query count from this client: '{{baseline}}'\n\nCurrent Domain or DNS query count from this client: '{{Total}}'\n\nDNS queries requested by this client inlcude: '{{DNSQueries}}'"
version: 1.0.2
kind: Scheduled