huntrule

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

Alerts when telnet/nmap/netcat-style binaries are executed on Linux via auditd, consistent with service discovery scanning.

FreeReviewedSigma · Low · v3
Product
linux
Service
auditd
Author
Alejandro Ortuno, oscd.community (SigmaHQ), DRL 1.1
Published
2020-10-21
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Discovery

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. 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
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
Malicious RDP Discovery Performed on Multiple Hosts (via rdp)
Malicious Anonymous Access Performed to Multiple Targets (via security)
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
  1. v3
    Candidate ingested via manual entry.2026-07-31
  2. v2
    Candidate ingested via manual entry.2026-07-31
  3. 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.