Detection rules › Kusto

TI Map URL Entity to AuditLogs

Severity
medium
Time window
14d
Group by
Id, ObservableValue, Url
Source
github.com/Azure/Azure-Sentinel

'This query identifies any URL indicators of compromise (IOCs) from threat intelligence (TI) by searching for matches in AuditLogs.'

MITRE ATT&CK coverage

TacticTechniques
Command & ControlT1071 Application Layer Protocol

Rule body kusto

id: 9991c277-e0a1-4079-8c40-fbfca2705615
name: TI Map URL Entity to AuditLogs
description: |
  'This query identifies any URL indicators of compromise (IOCs) from threat intelligence (TI) by searching for matches in AuditLogs.'
severity: Medium
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - AuditLogs
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: MicrosoftDefenderThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1071
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let AuditEvents = materialize(AuditLogs
    | where TimeGenerated >= ago(dt_lookBack)
    // Extract the URL that is contained within the JSON data
    | extend Url = extract("(http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]|[!*\\(\\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+)", 1,tostring(TargetResources))
    | extend userPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
    | extend TargetResourceDisplayName = tostring(TargetResources[0].displayName));
  let AuditUrls = AuditEvents | distinct Url = tolower(Url) | summarize make_list(Url);
  ThreatIntelIndicators
  //extract key part of kv pair
       | extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
       | where IndicatorType == "url"
       | extend Url = toupper(ObservableValue)
       | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
  | where TimeGenerated >= ago(ioc_lookBack)
  | where tolower(Url) in (AuditUrls)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
  | where IsActive and (ValidUntil > now() or isempty(ValidUntil))
  | extend Description = tostring(parse_json(Data).description)
  | where Description !contains_cs "State: inactive;" and Description !contains_cs "State: falsepos;"
  // using innerunique to keep perf fast and result set low, we only need one match to indicate potential malicious activity that needs to be investigated
  | join kind=innerunique (AuditEvents) on Url
  | where TimeGenerated < ValidUntil
  | summarize TimeGenerated = arg_max(TimeGenerated, *) by Id, Url
  | extend Description = tostring(parse_json(Data).description)
  | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
  | project TimeGenerated, Description, ActivityGroupNames, Id, Type, ValidUntil, Confidence,
  OperationName, Identity, userPrincipalName, TargetResourceDisplayName, Url
  | extend AccountName = tostring(split(userPrincipalName, "@")[0]), AccountUPNSuffix = tostring(split(userPrincipalName, "@")[1])
  | extend HostName = tostring(split(TargetResourceDisplayName, ".")[0]), DomainIndex = toint(indexof(TargetResourceDisplayName, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(TargetResourceDisplayName, DomainIndex + 1), TargetResourceDisplayName)
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: userPrincipalName
      - identifier: Name
        columnName: AccountName
      - identifier: UPNSuffix
        columnName: AccountUPNSuffix
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: TargetResourceDisplayName
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: HostNameDomain
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
version: 1.2.10
kind: Scheduled

Stages and Predicates

Parameters

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

Let binding: AuditEvents

let AuditEvents = materialize(AuditLogs
  | where TimeGenerated >= ago(dt_lookBack)
  | extend Url = extract("(http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]|[!*\\(\\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+)", 1,tostring(TargetResources))
  | extend userPrincipalName = tostring(parse_json(tostring(InitiatedBy.user)).userPrincipalName)
  | extend TargetResourceDisplayName = tostring(TargetResources[0].displayName));

Derived from dt_lookBack.

Let binding: AuditUrls

let AuditUrls = AuditEvents | distinct Url = tolower(Url) | summarize make_list(Url);

Derived from AuditEvents.

Stage 1: source

ThreatIntelIndicators

Stage 2: extend

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

Stage 3: where

| where IndicatorType == "url"

Stage 4: extend

| extend Url = toupper(ObservableValue)

Stage 5: extend

| extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)

Stage 6: where

| where TimeGenerated >= ago(ioc_lookBack)

Stage 7: where

| where tolower(Url) in (AuditUrls)

References AuditUrls (defined above).

Stage 8: summarize

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

Stage 9: where

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

Stage 10: extend

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

Stage 11: where

| where Description !contains_cs "State: inactive;" and Description !contains_cs "State: falsepos;"

Stage 12: join

| join kind=innerunique (AuditEvents) on Url

Stage 13: where

| where TimeGenerated < ValidUntil

Stage 14: summarize

| summarize TimeGenerated = arg_max(TimeGenerated, *) by Id, Url

Stage 15: extend

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

Stage 16: extend

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

Stage 17: project

| project TimeGenerated, Description, ActivityGroupNames, Id, Type, ValidUntil, Confidence,
OperationName, Identity, userPrincipalName, TargetResourceDisplayName, Url

Stage 18: extend (3 consecutive steps)

| extend AccountName = tostring(split(userPrincipalName, "@")[0]), AccountUPNSuffix = tostring(split(userPrincipalName, "@")[1])
| extend HostName = tostring(split(TargetResourceDisplayName, ".")[0]), DomainIndex = toint(indexof(TargetResourceDisplayName, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(TargetResourceDisplayName, DomainIndex + 1), TargetResourceDisplayName)

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
DescriptioncontainsState: falsepos;
DescriptioncontainsState: inactive;

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.

FieldKindValues
IndicatorTypeeq
  • url transforms: cased
TimeGeneratedlt
  • ValidUntil transforms: cased
Urlin
  • AuditUrls transforms: tolower, cased
ValidUntilis_null
  • (no value, null check)

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.

FieldSource
ActivityGroupNamesproject
Confidenceproject
Descriptionproject
Idproject
Identityproject
OperationNameproject
TargetResourceDisplayNameproject
TimeGeneratedproject
Typeproject
Urlproject
ValidUntilproject
userPrincipalNameproject
AccountNameextend
AccountUPNSuffixextend
DomainIndexextend
HostNameextend
HostNameDomainextend