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

id: 5b8344eb-fa28-4ac3-bcff-bc19d5d63089
name: Detect DNS queries reporting multiple errors from different clients - Static threshold based (ASIM DNS Solution)
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.'
severity: Medium
status: Available 
tags:
  - Schema: ASimDns
    SchemaVersion: 0.1.6
requiredDataConnectors: []
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1568
  - T1573
  - T1008
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)
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 
eventGroupingSettings:
  aggregationKind: SingleAlert
customDetails:
  SrcIPs: SrcIPs
  IPCountthreshold: IPCountthreshold
  TotalIPs: TotalIPs
alertDetailsOverride:
  alertDisplayNameFormat: "[Static threshold] 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. \n\nThreshold for total clients reporting errors: '{{IPCountthreshold}}'\n\nCurrent count of clients reporting errors for this DNS query: '{{TotalIPs}}'\n\nClients requesting this DNSQuery include:\n\n'{{SrcIPs}}'"
version: 1.0.4
kind: Scheduled