Potential DGADomain Generation Algorithm detected via Repetitive Failures - Static threshold based ASIM DNS Solution

let threshold = 100;
let lookback = 10d;
let referenceendtime = 1d;
let nxDomainDnsEvents = (stime: datetime, etime: datetime) {
  _Im_Dns(responsecodename='NXDOMAIN', starttime=stime, endtime=etime)
  | where DnsQueryTypeName in ("A", "AAAA")
  | where ipv4_is_match("127.0.0.1", SrcIpAddr) == False
  | where DnsQuery !contains "/" and DnsQuery contains "."
};
nxDomainDnsEvents (stime=ago(referenceendtime), etime=now())
| summarize
  StartTimeUtc = min(TimeGenerated),
  EndTimeUtc = max(TimeGenerated),
  DNSQueryCount=dcount(DnsQuery)
  by SrcIpAddr
| where DNSQueryCount > threshold
// Filter out previously seen IPs
| join kind=leftanti (nxDomainDnsEvents (stime=ago(lookback), etime=ago(referenceendtime))
  | summarize DNSQueryCount=dcount(DnsQuery) by SrcIpAddr, bin(TimeGenerated,1d)
  | where DNSQueryCount > threshold)
  on SrcIpAddr
// Pull out sample NXDomain responses for those remaining potentially infected IPs
| join kind = inner (nxDomainDnsEvents (stime=ago(lookback), etime=now())
  | summarize by DnsQuery, SrcIpAddr)
  on SrcIpAddr
| summarize
  StartTimeUtc = min(StartTimeUtc),
  EndTimeUtc = max(EndTimeUtc),
  DNSQueries=make_list(DnsQuery, 100)
  by SrcIpAddr, DNSQueryCount
| extend DNSQueryThreshold=threshold

relevantTechniques:
- T1568
- T1008
tactics:
- CommandAndControl
entityMappings:
- fieldMappings:
  - columnName: SrcIpAddr
    identifier: Address
  entityType: IP
status: Available
triggerOperator: gt
description: |
  'This rule identifies clients with a high NXDomain count, which could be indicative of a DGA (cycling through possible C2 domains where most C2s are not live). An alert is generated when a new IP address is seen (based on not being seen associated with NXDomain records in prior 10-day baseline period). It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
triggerThreshold: 0
name: Potential DGA(Domain Generation Algorithm) detected via Repetitive Failures - Static threshold based (ASIM DNS Solution)
customDetails:
  DNSQueries: DNSQueries
  DNSQueryThreshold: DNSQueryThreshold
  DNSQueryCount: DNSQueryCount
queryFrequency: 1d
id: 89ba52fa-96a7-4653-829a-ca49bb13336c
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS%20Essentials/Analytic%20Rules/PotentialDGADetectedviaRepetitiveFailuresStaticThresholdBased.yaml
version: 1.0.2
requiredDataConnectors: []
queryPeriod: 10d
kind: Scheduled
severity: Medium
query: |
  let threshold = 100;
  let lookback = 10d;
  let referenceendtime = 1d;
  let nxDomainDnsEvents = (stime: datetime, etime: datetime) {
    _Im_Dns(responsecodename='NXDOMAIN', starttime=stime, endtime=etime)
    | where DnsQueryTypeName in ("A", "AAAA")
    | where ipv4_is_match("127.0.0.1", SrcIpAddr) == False
    | where DnsQuery !contains "/" and DnsQuery contains "."
  };
  nxDomainDnsEvents (stime=ago(referenceendtime), etime=now())
  | summarize
    StartTimeUtc = min(TimeGenerated),
    EndTimeUtc = max(TimeGenerated),
    DNSQueryCount=dcount(DnsQuery)
    by SrcIpAddr
  | where DNSQueryCount > threshold
  // Filter out previously seen IPs
  | join kind=leftanti (nxDomainDnsEvents (stime=ago(lookback), etime=ago(referenceendtime))
    | summarize DNSQueryCount=dcount(DnsQuery) by SrcIpAddr, bin(TimeGenerated,1d)
    | where DNSQueryCount > threshold)
    on SrcIpAddr
  // Pull out sample NXDomain responses for those remaining potentially infected IPs
  | join kind = inner (nxDomainDnsEvents (stime=ago(lookback), etime=now())
    | summarize by DnsQuery, SrcIpAddr)
    on SrcIpAddr
  | summarize
    StartTimeUtc = min(StartTimeUtc),
    EndTimeUtc = max(EndTimeUtc),
    DNSQueries=make_list(DnsQuery, 100)
    by SrcIpAddr, DNSQueryCount
  | extend DNSQueryThreshold=threshold
tags:
- Schema: ASimDns
  SchemaVersion: 0.1.6
alertDetailsOverride:
  alertDisplayNameFormat: "[Static threshold] 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.

    DGA DNS query count baseline is: '{{DNSQueryThreshold}}'

    Current failed DNS query count from this client: '{{DNSQueryCount}}'

    DNS queries requested by this client inlcude: '{{DNSQueries}}'
eventGroupingSettings:
  aggregationKind: AlertPerResult

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/89ba52fa-96a7-4653-829a-ca49bb13336c')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/89ba52fa-96a7-4653-829a-ca49bb13336c')]",
      "properties": {
        "alertDetailsOverride": {
          "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\nDGA DNS query count baseline is: '{{DNSQueryThreshold}}'\n\nCurrent failed DNS query count from this client: '{{DNSQueryCount}}'\n\nDNS queries requested by this client inlcude: '{{DNSQueries}}'",
          "alertDisplayNameFormat": "[Static threshold] Potential DGA (Domain Generation Algorithm) originating from client IP: '{{SrcIpAddr}}' has been detected."
        },
        "alertRuleTemplateName": "89ba52fa-96a7-4653-829a-ca49bb13336c",
        "customDetails": {
          "DNSQueries": "DNSQueries",
          "DNSQueryCount": "DNSQueryCount",
          "DNSQueryThreshold": "DNSQueryThreshold"
        },
        "description": "'This rule identifies clients with a high NXDomain count, which could be indicative of a DGA (cycling through possible C2 domains where most C2s are not live). An alert is generated when a new IP address is seen (based on not being seen associated with NXDomain records in prior 10-day baseline period). It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'\n",
        "displayName": "Potential DGA(Domain Generation Algorithm) detected via Repetitive Failures - Static threshold based (ASIM DNS Solution)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SrcIpAddr",
                "identifier": "Address"
              }
            ]
          }
        ],
        "eventGroupingSettings": {
          "aggregationKind": "AlertPerResult"
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS%20Essentials/Analytic%20Rules/PotentialDGADetectedviaRepetitiveFailuresStaticThresholdBased.yaml",
        "query": "let threshold = 100;\nlet lookback = 10d;\nlet referenceendtime = 1d;\nlet nxDomainDnsEvents = (stime: datetime, etime: datetime) {\n  _Im_Dns(responsecodename='NXDOMAIN', starttime=stime, endtime=etime)\n  | where DnsQueryTypeName in (\"A\", \"AAAA\")\n  | where ipv4_is_match(\"127.0.0.1\", SrcIpAddr) == False\n  | where DnsQuery !contains \"/\" and DnsQuery contains \".\"\n};\nnxDomainDnsEvents (stime=ago(referenceendtime), etime=now())\n| summarize\n  StartTimeUtc = min(TimeGenerated),\n  EndTimeUtc = max(TimeGenerated),\n  DNSQueryCount=dcount(DnsQuery)\n  by SrcIpAddr\n| where DNSQueryCount > threshold\n// Filter out previously seen IPs\n| join kind=leftanti (nxDomainDnsEvents (stime=ago(lookback), etime=ago(referenceendtime))\n  | summarize DNSQueryCount=dcount(DnsQuery) by SrcIpAddr, bin(TimeGenerated,1d)\n  | where DNSQueryCount > threshold)\n  on SrcIpAddr\n// Pull out sample NXDomain responses for those remaining potentially infected IPs\n| join kind = inner (nxDomainDnsEvents (stime=ago(lookback), etime=now())\n  | summarize by DnsQuery, SrcIpAddr)\n  on SrcIpAddr\n| summarize\n  StartTimeUtc = min(StartTimeUtc),\n  EndTimeUtc = max(EndTimeUtc),\n  DNSQueries=make_list(DnsQuery, 100)\n  by SrcIpAddr, DNSQueryCount\n| extend DNSQueryThreshold=threshold\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P10D",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl"
        ],
        "tags": [
          {
            "Schema": "ASimDns",
            "SchemaVersion": "0.1.6"
          }
        ],
        "techniques": [
          "T1008",
          "T1568"
        ],
        "templateVersion": "1.0.2",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}