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

Status: available
Severity: medium
Time window: 10m
Group by: DnsQuery, DomainName, Dvc, IPCountthreshold, ResourceId, SrcIP, SrcIPs, TotalIPs
Source: github.com/Azure/Azure-Sentinel

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 normalization and is applied to any source that supports the ASIM DNS schema.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1008` Fallback Channels, `T1568` Dynamic Resolution, `T1573` Encrypted Channel

Event coverage

Provider	Event	Title
Sysmon	Event ID 22	DNSEvent (DNS query)

Rule body kusto

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

Stages and Predicates

Parameters

let lookback = 1h;
let threshold = 2;
let errors = dynamic(['NXDOMAIN', 'SERVFAIL', 'REFUSED']);

Stage 1: `source`

_Im_Dns(starttime=ago(lookback))

Stage 2: `where`

| where EventResultDetails has_any (errors)

Stage 3: `summarize`

| summarize SrcIPs = make_set(SrcIpAddr, 100), Dvcs = make_set(Dvc, 100), ResourceIds = make_set(_ResourceId, 100) by DnsQuery, bin(TimeGenerated, 10min)

Threshold: ge 2

Stage 4: `where`

| where array_length(SrcIPs) >= threshold

Stage 5: `extend`

| extend TotalIPs = array_length(SrcIPs),IPCountthreshold = threshold

Stage 6: `extend`

| extend DomainName = strcat(split(DnsQuery, ".")[1], ".", split(DnsQuery, ".")[2])

Stage 7: `mv-expand`

| mv-expand SrcIPs

Stage 8: `extend`

| extend SrcIP = tostring(SrcIPs)

Stage 9: `mv-expand`

| mv-expand Dvcs

Stage 10: `extend`

| extend Dvc = tostring(Dvcs)

Stage 11: `mv-expand`

| mv-expand ResourceIds

Stage 12: `extend`

| extend ResourceId = tostring(ResourceIds)

Stage 13: `extend`

| extend Dvc = strcat(split(Dvc, ".")[0])

Stage 14: `summarize`

| summarize Start=min(TimeGenerated), End=max(TimeGenerated) by SrcIP, Dvc, ResourceId, DnsQuery, DomainName, SrcIPs = tostring(SrcIPs), IPCountthreshold = threshold, TotalIPs

Stage 15: `extend`

| extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))

Stage 16: `extend`

| extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)

HostNameDomain =

ifDomainIndex != -1substring(Dvc, (DomainIndex + 1))

elseDvc

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`EventResultDetails`	match	`NXDOMAIN` `REFUSED` `SERVFAIL`
`SrcIPs`	ge	`2` transforms: `array_length`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`DnsQuery`	`summarize`
`DomainName`	`summarize`
`Dvc`	`summarize`
`End`	`summarize`
`IPCountthreshold`	`summarize`
`ResourceId`	`summarize`
`SrcIP`	`summarize`
`SrcIPs`	`summarize`
`Start`	`summarize`
`TotalIPs`	`summarize`
`DomainIndex`	`extend`
`HostName`	`extend`
`HostNameDomain`	`extend`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

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

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `summarize`

Stage 4: `where`

Stage 5: `extend`

Stage 6: `extend`

Stage 7: `mv-expand`

Stage 8: `extend`

Stage 9: `mv-expand`

Stage 10: `extend`

Stage 11: `mv-expand`

Stage 12: `extend`

Stage 13: `extend`

Stage 14: `summarize`

Stage 15: `extend`

Stage 16: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

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

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: summarize

Stage 4: where

Stage 5: extend

Stage 6: extend

Stage 7: mv-expand

Stage 8: extend

Stage 9: mv-expand

Stage 10: extend

Stage 11: mv-expand

Stage 12: extend

Stage 13: extend

Stage 14: summarize

Stage 15: extend

Stage 16: extend

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `summarize`

Stage 4: `where`

Stage 5: `extend`

Stage 6: `extend`

Stage 7: `mv-expand`

Stage 8: `extend`

Stage 9: `mv-expand`

Stage 10: `extend`

Stage 11: `mv-expand`

Stage 12: `extend`

Stage 13: `extend`

Stage 14: `summarize`

Stage 15: `extend`

Stage 16: `extend`