Detect DNS queries reporting multiple errors from different clients - Static threshold based ASIM DNS Solution

let lookback=1h;
let threshold = 2;
let errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']); 
_Im_Dns(starttime=ago(lookback)) 
  | where EventResultDetails has_any (errors) 
  | summarize SrcIPs = make_set(SrcIpAddr, 100), Dvcs = make_set(Dvc, 100), ResourceIds = make_set(_ResourceId, 100) by DnsQuery, bin(TimeGenerated, 10min) 
  | where array_length(SrcIPs) >= threshold 
  | extend TotalIPs = array_length(SrcIPs),IPCountthreshold = threshold 
  | extend DomainName = strcat(split(DnsQuery, ".")[1], ".", split(DnsQuery, ".")[2])  
  | mv-expand SrcIPs  
  | extend SrcIP = tostring(SrcIPs)  
  | mv-expand Dvcs  
  | extend Dvc = tostring(Dvcs)  
  | mv-expand ResourceIds  
  | extend ResourceId = tostring(ResourceIds)  
  | extend Dvc = strcat(split(Dvc, ".")[0])
  | summarize Start=min(TimeGenerated), End=max(TimeGenerated) by SrcIP, Dvc, ResourceId, DnsQuery, DomainName, SrcIPs = tostring(SrcIPs), IPCountthreshold = threshold, TotalIPs
  | extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)

name: Detect DNS queries reporting multiple errors from different clients - Static threshold based (ASIM DNS Solution)
severity: Medium
description: |
    'This rule creates an alert when multiple clients report errors for the same DNS query. This helps in identifying possible similar C2 communications originating from different clients. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
version: 1.0.4
customDetails:
  SrcIPs: SrcIPs
  TotalIPs: TotalIPs
  IPCountthreshold: IPCountthreshold
requiredDataConnectors: []
tactics:
- CommandAndControl
relevantTechniques:
- T1568
- T1573
- T1008
triggerThreshold: 0
entityMappings:
- entityType: DNS
  fieldMappings:
  - identifier: DomainName
    columnName: DnsQuery
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: SrcIP
- entityType: AzureResource
  fieldMappings:
  - identifier: ResourceId
    columnName: ResourceId
- entityType: Url
  fieldMappings:
  - identifier: Url
    columnName: DnsQuery
- entityType: Host
  fieldMappings:
  - identifier: HostName
    columnName: HostName
  - identifier: NTDomain
    columnName: HostNameDomain
kind: Scheduled
tags:
- Schema: ASimDns
  SchemaVersion: 0.1.6
status: Available
queryPeriod: 1h
alertDetailsOverride:
  alertDescriptionFormat: |-
    Multiple errors were detected on different clients for the same DNS query. These unsuccessful responses can be an indication of C2 communication. 

    Threshold for total clients reporting errors: '{{IPCountthreshold}}'

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

    Clients requesting this DNSQuery include:

    '{{SrcIPs}}'    
  alertDisplayNameFormat: "[Static threshold] Multiple errors for the same DNS query has been detected - '{{DnsQuery}}'"
triggerOperator: gt
query: |
  let lookback=1h;
  let threshold = 2;
  let errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']); 
  _Im_Dns(starttime=ago(lookback)) 
    | where EventResultDetails has_any (errors) 
    | summarize SrcIPs = make_set(SrcIpAddr, 100), Dvcs = make_set(Dvc, 100), ResourceIds = make_set(_ResourceId, 100) by DnsQuery, bin(TimeGenerated, 10min) 
    | where array_length(SrcIPs) >= threshold 
    | extend TotalIPs = array_length(SrcIPs),IPCountthreshold = threshold 
    | extend DomainName = strcat(split(DnsQuery, ".")[1], ".", split(DnsQuery, ".")[2])  
    | mv-expand SrcIPs  
    | extend SrcIP = tostring(SrcIPs)  
    | mv-expand Dvcs  
    | extend Dvc = tostring(Dvcs)  
    | mv-expand ResourceIds  
    | extend ResourceId = tostring(ResourceIds)  
    | extend Dvc = strcat(split(Dvc, ".")[0])
    | summarize Start=min(TimeGenerated), End=max(TimeGenerated) by SrcIP, Dvc, ResourceId, DnsQuery, DomainName, SrcIPs = tostring(SrcIPs), IPCountthreshold = threshold, TotalIPs
    | extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
    | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)  
eventGroupingSettings:
  aggregationKind: SingleAlert
queryFrequency: 1h
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/MultipleErrorsReportedForSameDNSQueryStaticThresholdBased.yaml
id: 5b8344eb-fa28-4ac3-bcff-bc19d5d63089