huntrule

Linux awk/gawk/mawk/nawk CommandLine invoking shell via system()

Flags awk/gawk/mawk/nawk command lines using BEGIN {system(...)} to spawn a shell on Linux.

FreeReviewedSigma · High · v3
Product
linux
Category
process_creation
Author
Li Ling, Andy Parkidomo, Robert Rakowski, Blake Hartstein (Bloomberg L.P.) (SigmaHQ), DRL 1.1
Published
2024-09-02
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Execution

  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 identifies Linux process executions where awk-family binaries are started with a command line containing a BEGIN block that calls system(), and the command line also references common shell binaries. Such behavior can indicate attempts to run arbitrary shell commands from within text-processing utilities, which attackers may use for execution and further escalation. Telemetry required includes Linux process creation events with the process image path and full command line content.

Reporting behind it

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Malicious IIS Worker Process Spawning Command Shell after ASP.NET ViewState Injection (via process_creation)
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Linux awk/gawk/mawk/nawk CommandLine invoking shell via system()
Pivot detection · T1059 · 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.