OpenCanary - Nmap NULL Scan Targeting Detected

Detects OpenCanary logtype 5003 events consistent with NMAP NULL scan targeting.

FreeReviewedSigma · High · v5

Product: opencanary
Category: application
Author: Marco Pedrinazzi (@pedrinazziM) (SigmaHQ), DRL 1.1
Published: 2026-01-06
Updated: 2026-07-31

ATT&CK techniques

Discovery

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
- T1046Network Service Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

Detects OpenCanary events indicating the node was targeted by an Nmap NULL scan. Such scans probe services with atypical packet patterns to identify exposed systems and available ports, which can precede broader reconnaissance. The rule relies on OpenCanary application telemetry with logtype 5003 indicating this specific scan behavior.

Reporting behind it

Related detections9 linkedT1046 — drag to rearrange

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Suspicious Network Reconnaissance via Advanced Port Scanner

Suspicious Nmap Scanner Probe URIs in HTTP Requests (via webserver)

Suspicious Internet Scanning for Docker and Kubelet Ports via masscan

Suspicious Fscan Internal Network Scanner Execution (via process_creation)

Possible Network Service Scanning via Nmap or Masscan (via process_creation)

Malicious Anonymous Login - Domain Specified (via security)

Suspicious Network Scanning Tool Execution

OpenCanary - Nmap NULL Scan Targeting Detected

Pivot detection · T1046 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

opencanary-nmap-null-scan-targeting-logtype-5003-68b8547b

title: OpenCanary - Nmap NULL Scan Targeting Detected
id: 3686e3ee-4b0f-47f2-8925-df9870dc8c9b
status: experimental
description: Detects OpenCanary events indicating the node was targeted by an Nmap NULL scan. Such scans probe services with atypical packet patterns to identify exposed systems and available ports, which can precede broader reconnaissance. The rule relies on OpenCanary application telemetry with logtype 5003 indicating this specific scan behavior.
references:
  - https://opencanary.readthedocs.io/en/latest/starting/configuration.html#services-configuration
  - https://github.com/thinkst/opencanary/blob/a0896adfcaf0328cfd5829fe10d2878c7445138e/opencanary/logger.py#L52
  - https://github.com/SigmaHQ/sigma/blob/master/rules/application/opencanary/opencanary_portscan_nmap_null_scan.yml
author: Marco Pedrinazzi (@pedrinazziM), Huntrule Team
date: 2026-01-06
tags:
  - attack.discovery
  - attack.t1046
logsource:
  category: application
  product: opencanary
detection:
  selection:
    logtype: 5003
  condition: selection
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: 68b8547b-107f-43f3-97fb-900a7d63c190
    type: derived

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