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

Requête originale, sans modification.

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 
      (
          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(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*
),
(
      DNSEssentialsCustomParser
      | where Type in ("DNS_Summarized_Logs_ip_CL", "DNS_Summarized_Logs_ipV1_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