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Detection rules › Kusto

NGINX - Request to sensitive files

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

'Detects request to sensitive files.'

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1189 Drive-by Compromise

Rule body kusto

id: 2141ef6c-d158-4d44-b739-b145a4c21947
name: NGINX - Request to sensitive files
description: |
  'Detects request to sensitive files.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: CustomLogsAma
    dataTypes:
      - NGINX_CL
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1189
query: |
  let forbidden_files = dynamic(['shadow', 'passwd', 'id_rsa']);
  NGINXHTTPServer
  | extend File = extract(@"(.*\/)?(.*)", 2, tostring(UrlOriginal))
  | where File in (forbidden_files)
  | extend FileCustomEntity = File, UrlCustomEntity = UrlOriginal
entityMappings:
  - entityType: File
    fieldMappings:
      - identifier: Name
        columnName: FileCustomEntity
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: UrlCustomEntity
version: 1.0.2
kind: Scheduled

Stages and Predicates

Parameters

let forbidden_files = dynamic(['shadow', 'passwd', 'id_rsa']);

Stage 1: source

NGINXHTTPServer

Stage 2: extend

| extend File = extract(@"(.*\/)?(.*)", 2, tostring(UrlOriginal))

Stage 3: where

| where File in (forbidden_files)

Stage 4: extend

| extend FileCustomEntity = File, UrlCustomEntity = UrlOriginal

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
Filein
  • id_rsa transforms: cased
  • passwd transforms: cased
  • shadow 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
Fileextend
FileCustomEntityextend
UrlCustomEntityextend