Potential DGA detected ASIM DNS Schema

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Id	983a6922-894d-413c-9f04-d7add0ecc307
Rulename	Potential DGA detected (ASIM DNS Schema)
Description	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). 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). This analytic rule uses ASIM and supports any built-in or custom source that supports the ASIM DNS schema
Severity	Medium
Tactics	CommandAndControl
Techniques	T1568 T1008
Required data connectors	AzureFirewall CiscoUmbrellaDataConnector Corelight DNS GCPDNSDataConnector InfobloxNIOS NXLogDnsLogs Zscaler
Kind	Scheduled
Query frequency	1d
Query period	10d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimDNS/imDns_HighNXDomainCount_detection.yaml
Version	1.3.4
Arm template	983a6922-894d-413c-9f04-d7add0ecc307.json

KQL

let referencestarttime = 10d;
let referenceendtime = 1d;
let threshold = 100;
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())
  | extend sld = tostring(split(DnsQuery, ".")[-2])
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), dcount(sld) by SrcIpAddr
  | where dcount_sld > threshold
  // Filter out previously seen IPs
  | join kind=leftanti (nxDomainDnsEvents (stime=ago(referencestarttime), etime=ago(referenceendtime))
    | extend sld = tostring(split(DnsQuery, ".")[-2])
    | summarize dcount(sld) by SrcIpAddr
    | where dcount_sld > threshold ) on SrcIpAddr
// Pull out sample NXDomain responses for those remaining potentially infected IPs
| join kind = inner (nxDomainDnsEvents (stime=ago(referencestarttime), etime=now()) | summarize by DnsQuery, SrcIpAddr) on SrcIpAddr
| summarize StartTime = min(StartTime), EndTime = max(EndTime), sampleNXDomainList=make_list(DnsQuery, 100)  by SrcIpAddr, dcount_sld

YAML

queryPeriod: 10d
query: |
  let referencestarttime = 10d;
  let referenceendtime = 1d;
  let threshold = 100;
  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())
    | extend sld = tostring(split(DnsQuery, ".")[-2])
    | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), dcount(sld) by SrcIpAddr
    | where dcount_sld > threshold
    // Filter out previously seen IPs
    | join kind=leftanti (nxDomainDnsEvents (stime=ago(referencestarttime), etime=ago(referenceendtime))
      | extend sld = tostring(split(DnsQuery, ".")[-2])
      | summarize dcount(sld) by SrcIpAddr
      | where dcount_sld > threshold ) on SrcIpAddr
  // Pull out sample NXDomain responses for those remaining potentially infected IPs
  | join kind = inner (nxDomainDnsEvents (stime=ago(referencestarttime), etime=now()) | summarize by DnsQuery, SrcIpAddr) on SrcIpAddr
  | summarize StartTime = min(StartTime), EndTime = max(EndTime), sampleNXDomainList=make_list(DnsQuery, 100)  by SrcIpAddr, dcount_sld  
name: Potential DGA detected (ASIM DNS Schema)
entityMappings:
- fieldMappings:
  - columnName: SrcIpAddr
    identifier: Address
  entityType: IP
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimDNS/imDns_HighNXDomainCount_detection.yaml
tags:
- ParentAlert: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/DnsEvents/DNS_HighNXDomainCount_detection.yaml
  version: 1.0.0
- SchemaVersion: 0.1.1
  Schema: ASIMDns
requiredDataConnectors:
- connectorId: DNS
  dataTypes:
  - DnsEvents
- connectorId: AzureFirewall
  dataTypes:
  - AzureDiagnostics
- connectorId: Zscaler
  dataTypes:
  - CommonSecurityLog
- connectorId: InfobloxNIOS
  dataTypes:
  - Syslog
- connectorId: GCPDNSDataConnector
  dataTypes:
  - GCP_DNS_CL
- connectorId: NXLogDnsLogs
  dataTypes:
  - NXLog_DNS_Server_CL
- connectorId: CiscoUmbrellaDataConnector
  dataTypes:
  - Cisco_Umbrella_dns_CL
- connectorId: Corelight
  dataTypes:
  - Corelight_CL
description: |
  '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). 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).
  This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM DNS schema'  
kind: Scheduled
version: 1.3.4
metadata:
  author:
    name: Yaron
  categories:
    domains:
    - Security - Network
  support:
    tier: Community
  source:
    kind: Community
queryFrequency: 1d
severity: Medium
relevantTechniques:
- T1568
- T1008
triggerOperator: gt
triggerThreshold: 0
tactics:
- CommandAndControl
id: 983a6922-894d-413c-9f04-d7add0ecc307

ARM