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Detection rules › Kusto

Trust Monitor Event

Severity
medium
Time window
5m
Author
SecurityJedi
Source
github.com/Azure/Azure-Sentinel

'This query identifies when a new trust monitor event is detected.'

MITRE ATT&CK coverage

TacticTechniques
Credential AccessT1528 Steal Application Access Token, T1555 Credentials from Password Stores

Rule body kusto

id: 8dcf7238-a7d0-4cfd-8d0c-b230e3cd9182
name: Trust Monitor Event
description: |
  'This query identifies when a new trust monitor event is detected.'
severity: Medium
requiredDataConnectors: []
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1528
  - T1555
query: |
  let timeframe = ago(5m);
  DuoSecurityTrustMonitor_CL
  | where TimeGenerated >= timeframe
  | extend AccountName = tostring(split(surfaced_auth_user_name_s, "@")[0]), AccountUPNSuffix = tostring(split(surfaced_auth_user_name_s, "@")[1])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: surfaced_auth_user_name_s
      - identifier: Name
        columnName: AccountName
      - identifier: UPNSuffix
        columnName: AccountUPNSuffix
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: surfaced_auth_access_device_ip_s
version: 1.0.4
kind: Scheduled
metadata:
    source:
        kind: Community
    author:
        name: SecurityJedi
    support:
        tier: Community
    categories:
        domains: [ "Security - Others" ]

Stages and Predicates

Parameters

let timeframe = ago(5m);

Stage 1: source

DuoSecurityTrustMonitor_CL

Stage 2: where

| where TimeGenerated >= timeframe

Stage 3: extend

| extend AccountName = tostring(split(surfaced_auth_user_name_s, "@")[0]), AccountUPNSuffix = tostring(split(surfaced_auth_user_name_s, "@")[1])

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
TimeGeneratedge
  • timeframe transforms: cased

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
AccountNameextend
AccountUPNSuffixextend