TI Map Domain entity to Dns Events (ASIM DNS Schema)

Severity: medium
Time window: 14d
Group by: DnsQuery, DomainName, IndicatorId, ObservableValue
Source: github.com/Azure/Azure-Sentinel

Identifies a match in DNS events from any Domain IOC from TI This analytic rule uses ASIM and supports any built-in or custom source that supports the ASIM DNS schema'

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1071` Application Layer Protocol

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 22: DNSEvent (DNS query)

Rule body

id: 7c1ea2e6-6210-412c-92e4-180803a741b4
name: TI Map Domain entity to Dns Events (ASIM DNS Schema)
description: |
  Identifies a match in DNS events from any Domain IOC from TI
  This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM DNS schema'
severity: Medium
requiredDataConnectors:
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelIndicators
  - 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: MicrosoftDefenderThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: CiscoUmbrellaDataConnector
    dataTypes: 
      - Cisco_Umbrella_dns_CL
  - connectorId: Corelight
    dataTypes: 
      - Corelight_CL
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1071
tags:
  - Id: 85aca4d1-5d15-4001-abd9-acb86ca1786a
    version: 1.0.0
  - Schema: ASIMDns
    SchemaVersion: 0.1.1
query: |
  let HAS_ANY_MAX = 10000;
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let DomainTIs= ThreatIntelIndicators
    // Picking up only IOC's that contain the entities we want
    //extract key part of kv pair
    | extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
    | extend IndicatorId = tostring(split(Id, "--")[2])
    | where IndicatorType == "domain-name"
    | extend DomainName = ObservableValue
    | extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
    
    | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
    | extend ThreatList = tostring(parse_json(Data).indicator_types[0])
    | where TimeGenerated >= ago(ioc_lookBack)
    | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId, ObservableValue
    | where IsActive and (ValidUntil > now() or isempty(ValidUntil));
  let Domains = DomainTIs  |summarize NDomains=dcount(DomainName), DomainsList=make_set(DomainName) 
    | project DomainList = iff(NDomains > HAS_ANY_MAX, dynamic([]), DomainsList);
  DomainTIs
  | project-reorder *, ThreatList, IsActive, Tags, TrafficLightProtocolLevel, DomainName, Type
    | join (
        _Im_Dns(starttime=ago(dt_lookBack), domain_has_any=toscalar(Domains))
        | extend DNS_TimeGenerated = TimeGenerated
  ) on $left.DomainName==$right.DnsQuery
  | where DNS_TimeGenerated < ValidUntil
  | extend Description = tostring(parse_json(Data).description)
  | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
  | project LatestIndicatorTime, Description, ActivityGroupNames, IndicatorId, ValidUntil, Confidence, DNS_TimeGenerated, Dvc, SrcIpAddr, Domain, DnsQuery, DnsQueryType, Url
  | extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Dvc
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: HostNameDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
  - entityType: DNS
    fieldMappings:
      - identifier: DomainName
        columnName: Domain        
customDetails:
  LatestIndicatorTime: LatestIndicatorTime
  Description: Description
  ActivityGroupNames: ActivityGroupNames
  IndicatorId: IndicatorId
  ExpirationDateTime: ValidUntil
  ConfidenceScore: Confidence
  DNSRequestTime: DNS_TimeGenerated
  SourceIPAddress: SrcIpAddr
  DnsQuery: DnsQuery
  QueryType: DnsQueryType
version: 1.2.4
kind: Scheduled

Stages and Predicates

Parameters

let HAS_ANY_MAX = 10000;
let dt_lookBack = 1h;
let ioc_lookBack = 14d;

let DomainTIs is inlined into the numbered stages below.

Let binding: `Domains` used in Stage 10

let Domains = DomainTIs  |summarize NDomains=dcount(DomainName), DomainsList=make_set(DomainName) 
  | project DomainList = iff(NDomains > HAS_ANY_MAX, dynamic([]), DomainsList);

Stages 1 to 8 define let DomainTIs (the rule's main pipeline source); stages 9 to 16 run on it.

Stage 1: `source`

ThreatIntelIndicators

Stage 2: `extend`

| extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))

Stage 3: `extend`

| extend IndicatorId = tostring(split(Id, "--")[2])

Stage 4: `where`

| where IndicatorType == "domain-name"

Stage 5: `extend` (4 consecutive steps)

| extend DomainName = ObservableValue
| extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
| extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
| extend ThreatList = tostring(parse_json(Data).indicator_types[0])

Stage 6: `where`

| where TimeGenerated >= ago(ioc_lookBack)

Stage 7: `summarize`

| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId, ObservableValue

Stage 8: `where`

| where IsActive and (ValidUntil > now() or isempty(ValidUntil))

Stage 9: `project-reorder`

DomainTIs
| project-reorder *, ThreatList, IsActive, Tags, TrafficLightProtocolLevel, DomainName, Type

Stage 10: `join`

| join (
      _Im_Dns(starttime=ago(dt_lookBack), domain_has_any=toscalar(Domains))
      | extend DNS_TimeGenerated = TimeGenerated
) on $left.DomainName==$right.DnsQuery

Stage 11: `where`

| where DNS_TimeGenerated < ValidUntil

Stage 12: `extend`

| extend Description = tostring(parse_json(Data).description)

Stage 13: `extend`

| extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))

Stage 14: `project`

| project LatestIndicatorTime, Description, ActivityGroupNames, IndicatorId, ValidUntil, Confidence, DNS_TimeGenerated, Dvc, SrcIpAddr, Domain, DnsQuery, DnsQueryType, Url

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

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`DNS_TimeGenerated`	cross_field_compare	`ValidUntil` transforms: `op:lt` corpus 3 (kusto 3)	`field:"DNS_TimeGenerated" kind:cross_field_compare value:"ValidUntil"`
`IndicatorType`	eq	`domain-name` corpus 11 (kusto 11)	`field:"IndicatorType" kind:eq value:"domain-name"`
`ValidUntil`	is_null	(no value, null check)	`field:"ValidUntil" kind:is_null`

Output fields

These fields are emitted when the rule matches.

Field	Source
`ActivityGroupNames`	`project`
`Confidence`	`project`
`DNS_TimeGenerated`	`project`
`Description`	`project`
`DnsQuery`	`project`
`DnsQueryType`	`project`
`Domain`	`project`
`Dvc`	`project`
`IndicatorId`	`project`
`LatestIndicatorTime`	`project`
`SrcIpAddr`	`project`
`Url`	`project`
`ValidUntil`	`project`
`DomainIndex`	`extend`
`HostName`	`extend`
`HostNameDomain`	`extend`

TI Map Domain entity to Dns Events (ASIM DNS Schema)

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Parameters

Let binding: Domains used in Stage 10

Stage 1: source

Stage 2: extend

Stage 3: extend

Stage 4: where

Stage 5: extend (4 consecutive steps)

Stage 6: where

Stage 7: summarize

Stage 8: where

Stage 9: project-reorder

Stage 10: join

Stage 11: where

Stage 12: extend

Stage 13: extend

Stage 14: project

Stage 15: extend

Stage 16: extend