Excessive NXDOMAIN DNS Queries

Status: available
Severity: medium
Time window: 15m
Group by: SrcIpAddr
Source: github.com/Azure/Azure-Sentinel

'This creates an incident in the event a client generates excessive amounts of DNS queries for non-existent domains.'

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1008` Fallback Channels `T1568` Dynamic Resolution

Rule body

id: b8266f81-2715-41a6-9062-42486cbc9c73
name: Excessive NXDOMAIN DNS Queries
description: |
  'This creates an incident in the event a client generates excessive amounts of DNS queries for non-existent domains.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: SyslogAma
    datatypes:
      - Syslog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1568
  - T1008
query: |
  let threshold = 200;
  Infoblox_dnsclient
  | where isnotempty(DnsResponseCode)
  | where DnsResponseCode =~ "NXDOMAIN"
  | summarize count() by SrcIpAddr, bin(TimeGenerated,15m)
  | where count_ > threshold
  | join kind=inner (Infoblox_dnsclient
      | where isnotempty(DnsResponseCode)
      | where DnsResponseCode =~ "NXDOMAIN"
      ) on SrcIpAddr
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
version: 1.0.5
kind: Scheduled

Stages and Predicates

Parameters

let threshold = 200;

Stage 1: `source`

Infoblox_dnsclient

Stage 2: `where`

| where isnotempty(DnsResponseCode)

Stage 3: `where`

| where DnsResponseCode =~ "NXDOMAIN"

Stage 4: `summarize`

| summarize count() by SrcIpAddr, bin(TimeGenerated,15m)

Stage 5: `where`

| where count_ > threshold

Stage 6: `join`

| join kind=inner (Infoblox_dnsclient
    | where isnotempty(DnsResponseCode)
    | where DnsResponseCode =~ "NXDOMAIN"
    ) on SrcIpAddr

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`DnsResponseCode`	eq	`NXDOMAIN`	`field:"DnsResponseCode" kind:eq value:"NXDOMAIN"`
`DnsResponseCode`	is_not_null	(no value, null check)	`field:"DnsResponseCode" kind:is_not_null`
`count_`	gt	`200`	`field:"count_" kind:gt value:"200"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`SrcIpAddr`	`summarize`

Excessive NXDOMAIN DNS Queries

MITRE ATT&CK coverage

Rule body

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: summarize

Stage 5: where

Stage 6: join