Detection rules › Kusto
Port Scan Detected
'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 kusto
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
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
Src_IP | cidr_match | 10.0.0.0/8 |
Src_IP | cidr_match | 172.16.0.0/12 |
Src_IP | cidr_match | 192.168.0.0/16 |
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.
| Field | Kind | Values |
|---|---|---|
Log_Type | eq |
|
dcount_Dst_Port | gt |
|
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.
| Field | Source |
|---|---|
Src_IP | summarize |