Linux auditd: Network service enumeration via telnet, nmap, or netcat

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

This rule flags Linux auditd syscall events where the executing binary ends with telnet, nmap, netcat, nc, ncat, or nc.openbsd. Such tools are commonly used to enumerate local or remote network services, which can precede broader discovery and access attempts. Detection relies on auditd telemetry capturing SYSCALL events with the process executable path suffix.

Reporting behind it

Related detections9 linkedT1046 — drag to rearrange

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Malicious Network Login Performed to Multiple Targets (via security)

Suspicious SoftPerfect Network Scanner Execution for Discovery

Suspicious SoftPerfect Network Scanner Execution (via process_creation)

Linux auditd: Network service enumeration via telnet, nmap, or netcat

Pivot detection · T1046 · 9 related

Changelog

v3

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.

linux-auditd-process-executions-of-telnet-nmap-netcat-for-network-service-scanni-3761e026

title: "Linux auditd: Network service enumeration via telnet, nmap, or netcat"
id: d4d3414e-f718-4e8e-9419-ceaf7672f310
related:
  - id: 3e102cd9-a70d-4a7a-9508-403963092f31
    type: derived
  - id: 3761e026-f259-44e6-8826-719ed8079408
    type: derived
status: test
description: This rule flags Linux auditd syscall events where the executing binary ends with telnet, nmap, netcat, nc, ncat, or nc.openbsd. Such tools are commonly used to enumerate local or remote network services, which can precede broader discovery and access attempts. Detection relies on auditd telemetry capturing SYSCALL events with the process executable path suffix.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1046/T1046.md
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/auditd/syscall/lnx_auditd_network_service_scanning.yml
author: Alejandro Ortuno, oscd.community, Huntrule Team
date: 2020-10-21
modified: 2023-09-26
tags:
  - attack.discovery
  - attack.t1046
logsource:
  product: linux
  service: auditd
  definition: Configure these rules https://github.com/Neo23x0/auditd/blob/e181243a7c708e9d579557d6f80e0ed3d3483b89/audit.rules#L182-L183
detection:
  selection:
    type: SYSCALL
    exe|endswith:
      - /telnet
      - /nmap
      - /netcat
      - /nc
      - /ncat
      - /nc.openbsd
    key: network_connect_4
  condition: selection
falsepositives:
  - Legitimate administration activities
level: low
license: DRL-1.1

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