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Detection rules › Kusto

Trend Micro CAS - Suspicious filename

Status
available
Severity
medium
Time window
1h
Source
github.com/Azure/Azure-Sentinel

'Detects unexpected filename.'

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1566 Phishing

Rule body kusto

id: 52c4640a-1e2b-4155-b69e-e1869c9a57c9
name: Trend Micro CAS - Suspicious filename
description: |
  'Detects unexpected filename.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: TrendMicroCAS
    dataTypes:
      - TrendMicroCAS
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
query: |
  TrendMicroCAS
  | where isnotempty(SrcFileName)
  | where SrcFileName matches regex @'\A[a-zA-Z0-9_\-.]{1,3}\.\w+$'
  | extend AccountCustomEntity = DstUserName
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: AccountCustomEntity
version: 1.0.0
kind: Scheduled

Stages and Predicates

Stage 1: source

TrendMicroCAS

Stage 2: where

| where isnotempty(SrcFileName)

Stage 3: where

| where SrcFileName matches regex @'\A[a-zA-Z0-9_\-.]{1,3}\.\w+$'

Stage 4: extend

| extend AccountCustomEntity = DstUserName

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
SrcFileNameis_not_null
  • (no value, null check)
SrcFileNameregex_match
  • \A[a-zA-Z0-9_\-.]{1,3}.\w+$

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
AccountCustomEntityextend