Port Scan Detected

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

'This alert creates an incident when a source IP addresses attempt to communicate with a large amount of distinct ports within a short period.'

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1046` Network Service Discovery

Rule body

id: 427e4c9e-8cf4-4094-a684-a2d060dbca38
name: Port Scan Detected
description: |
  'This alert creates an incident when a source IP addresses attempt to communicate with a large amount of distinct ports within a short period.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: SyslogAma
    datatypes:
      - Syslog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Discovery
relevantTechniques:
  - T1046
query: |
  let threshold = 50;
  SophosXGFirewall
  | where Log_Type =~ "Firewall"
  | where not(ipv4_is_match("10.0.0.0",Src_IP,8) or ipv4_is_match("172.16.0.0",Src_IP,12) or ipv4_is_match("192.168.0.0",Src_IP,16))
  | summarize dcount(Dst_Port) by Src_IP, bin(TimeGenerated, 5m)
  | where dcount_Dst_Port > threshold
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: Src_IP
version: 1.0.4
kind: Scheduled

Stages and Predicates

Parameters

let threshold = 50;

Stage 1: `source`

SophosXGFirewall

Stage 2: `where`

| where Log_Type =~ "Firewall"

Stage 3: `where`

| where not(ipv4_is_match("10.0.0.0",Src_IP,8) or ipv4_is_match("172.16.0.0",Src_IP,12) or ipv4_is_match("192.168.0.0",Src_IP,16))

Stage 4: `summarize`

| summarize dcount(Dst_Port) by Src_IP, bin(TimeGenerated, 5m)

Stage 5: `where`

| where dcount_Dst_Port > threshold

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Src_IP`	cidr_match	`10.0.0.0/8`	`excludes:Src_IP` `field:"Src_IP" value:"10.0.0.0/8"`
`Src_IP`	cidr_match	`172.16.0.0/12`	`excludes:Src_IP` `field:"Src_IP" value:"172.16.0.0/12"`
`Src_IP`	cidr_match	`192.168.0.0/16`	`excludes:Src_IP` `field:"Src_IP" value:"192.168.0.0/16"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Log_Type`	eq	`Firewall`	`field:"Log_Type" kind:eq value:"Firewall"`
`dcount_Dst_Port`	gt	`50`	`field:"dcount_Dst_Port" kind:gt value:"50"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`Src_IP`	`summarize`