Port scan detected (ASIM Network Session schema)

Status: available
Severity: medium
Time window: 5m
Group by: SrcIpAddr
Source: github.com/Azure/Azure-Sentinel

This rule identifies a possible port scan, in which a single source tries to access a large number of different ports is a short time frame. This may indicate that a port scanner is trying to identify open ports in order to penetrate a system. This analytic rule uses ASIM and supports any built-in or custom source that supports the ASIM NetworkSession schema

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1046` Network Service Discovery

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 3: Network connection
Security-Auditing	Event ID 5152: The Windows Filtering Platform blocked a packet.
Security-Auditing	Event ID 5154: The Windows Filtering Platform has permitted an application or service to listen on a port for incoming connections.
Security-Auditing	Event ID 5155: The Windows Filtering Platform has blocked an application or service from listening on a port for incoming connections.
Security-Auditing	Event ID 5156: The Windows Filtering Platform has permitted a connection.
Security-Auditing	Event ID 5157: The Windows Filtering Platform has blocked a connection.
Security-Auditing	Event ID 5158: The Windows Filtering Platform has permitted a bind to a local port.
Security-Auditing	Event ID 5159: The Windows Filtering Platform has blocked a bind to a local port.

Rule body

id: 1da9853f-3dea-4ea9-b7e5-26730da3d537
name: Port scan detected  (ASIM Network Session schema)
description: |
  'This rule identifies a possible port scan, in which a single source tries to access a large number of different ports is a short time frame. This may indicate that a [port scanner](https://en.wikipedia.org/wiki/Port_scanner) is trying to identify open ports in order to penetrate a system.
  This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM NetworkSession schema'
alertDetailsOverride:
  alertDisplayNameFormat: Potential port scan from {{SrcIpAddr}}
  alertDescriptionFormat: A port scan has been performed from address {{SrcIpAddr}} over {{AttemptedPortsCount}} ports within 5 minutes. This may indicate that a [port scanner](https://en.wikipedia.org/wiki/Port_scanner) is trying to identify open ports in order to penetrate a system. 

severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: AWSS3
    dataTypes:
      - AWSVPCFlow
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceNetworkEvents
  - connectorId: SecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: WindowsSecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: WindowsForwardedEvents
    dataTypes:
      - WindowsEvent
  - connectorId: Zscaler
    dataTypes:
      - CommonSecurityLog
  - connectorId: MicrosoftSysmonForLinux
    dataTypes:
      - Syslog
  - connectorId: PaloAltoNetworks
    dataTypes:
      - CommonSecurityLog
  - connectorId: AzureMonitor(VMInsights)
    dataTypes:
      - VMConnection
  - connectorId: AzureFirewall
    dataTypes:
      - AzureDiagnostics
  - connectorId: AzureNSG
    dataTypes:
      - AzureDiagnostics
  - connectorId: CiscoASA
    dataTypes:
      - CommonSecurityLog
  - connectorId: CiscoAsaAma
    dataTypes:
      - CommonSecurityLog
  - connectorId: Corelight
    dataTypes:
      - Corelight_CL
  - connectorId: AIVectraStream
    dataTypes:
      - VectraStream
  - connectorId: CheckPoint
    dataTypes:
      - CommonSecurityLog
  - connectorId: Fortinet
    dataTypes:
      - CommonSecurityLog
  - connectorId: CiscoMeraki
    dataTypes:
      - Syslog
      - CiscoMerakiNativePoller

queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Discovery
relevantTechniques:
  - T1046
tags:
  - ParentAlert: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Sophos%20XG%20Firewall/Analytic%20Rules/PortScanDetected.yaml
    version: 1.0.0
  - Schema: ASimNetworkSessions
    SchemaVersion: 0.2.4
query: |
  let PortScanThreshold = 50;
  _Im_NetworkSession
  | where ipv4_is_private(SrcIpAddr) == False
  | where SrcIpAddr !in ("127.0.0.1", "::1")
  | summarize AttemptedPortsCount=dcount(DstPortNumber), AttemptedPorts=make_set(DstPortNumber, 100), ReportedBy=make_set(strcat(EventVendor, "/", EventProduct), 20) by SrcIpAddr, bin(TimeGenerated, 5m)
  | where AttemptedPortsCount > PortScanThreshold
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr

customDetails:
  AttemptedPortsCount: AttemptedPortsCount

version: 1.0.6
kind: Scheduled

Stages and Predicates

Parameters

let PortScanThreshold = 50;

Stage 1: `source`

_Im_NetworkSession

Stage 2: `where`

| where ipv4_is_private(SrcIpAddr) == False

Stage 3: `where`

| where SrcIpAddr !in ("127.0.0.1", "::1")

Stage 4: `summarize`

| summarize AttemptedPortsCount=dcount(DstPortNumber), AttemptedPorts=make_set(DstPortNumber, 100), ReportedBy=make_set(strcat(EventVendor, "/", EventProduct), 20) by SrcIpAddr, bin(TimeGenerated, 5m)

Stage 5: `where`

| where AttemptedPortsCount > PortScanThreshold

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`SrcIpAddr`	cidr_match	`10.0.0.0/8`, `172.16.0.0/12`, `192.168.0.0/16`, `169.254.0.0/16`, `127.0.0.0/8`	`excludes:SrcIpAddr`
`SrcIpAddr`	in	`127.0.0.1`, `::1`	`excludes:SrcIpAddr` `field:"SrcIpAddr" value:"127.0.0.1"` `field:"SrcIpAddr" value:"::1"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`AttemptedPortsCount`	gt	`50`	`field:"AttemptedPortsCount" kind:gt value:"50"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`AttemptedPorts`	`summarize`
`AttemptedPortsCount`	`summarize`
`ReportedBy`	`summarize`
`SrcIpAddr`	`summarize`