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Detection rules › Kusto

PaloAlto - Inbound connection to high risk ports

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

'Detects inbound connection to high risk ports.'

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1133 External Remote Services, T1190 Exploit Public-Facing Application

Rule body kusto

id: b2dd2dac-51c9-11ec-bf63-0242ac130002
name: PaloAlto - Inbound connection to high risk ports
description: |
  'Detects inbound connection to high risk ports.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: CefAma
    dataTypes:
      - CommonSecurityLog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1190
  - T1133
query: |
  let HighRiskPorts = dynamic(['21', '22', '23', '25', '53', '443', '110', '135', '137', '138', '139', '1433', '1434']);
  PaloAltoCDLEvent
  | where EventResourceId =~ 'TRAFFIC'
  | where ipv4_is_private(SrcIpAddr) == false
  | where DstPortNumber in (HighRiskPorts)
  | extend IPCustomEntity = SrcIpAddr
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IPCustomEntity
version: 1.0.3
kind: Scheduled

Stages and Predicates

Parameters

let HighRiskPorts = dynamic(['21', '22', '23', '25', '53', '443', '110', '135', '137', '138', '139', '1433', '1434']);

Stage 1: source

PaloAltoCDLEvent

Stage 2: where

| where EventResourceId =~ 'TRAFFIC'

Stage 3: where

| where ipv4_is_private(SrcIpAddr) == false

Stage 4: where

| where DstPortNumber in (HighRiskPorts)

Stage 5: extend

| extend IPCustomEntity = SrcIpAddr

Exclusions

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

FieldKindExcluded values
SrcIpAddrcidr_match10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16, 127.0.0.0/8

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
DstPortNumberin
  • 110 transforms: cased
  • 135 transforms: cased
  • 137 transforms: cased
  • 138 transforms: cased
  • 139 transforms: cased
  • 1433 transforms: cased
  • 1434 transforms: cased
  • 21 transforms: cased
  • 22 transforms: cased
  • 23 transforms: cased
  • 25 transforms: cased
  • 443 transforms: cased
  • 53 transforms: cased
EventResourceIdeq
  • TRAFFIC

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
IPCustomEntityextend