Linux Inline Python (-c) Calling os.system to Spawn Shell

Flags Linux processes launching inline Python (-c) that invokes os.system() to execute a shell.

FreeReviewedSigma · High · v2

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

ATT&CK techniques

Execution

Recon
Resource Dev
Initial Access
Execution
- T1059Command and Scripting Interpreter
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Linux process creation where the command line includes inline Python execution via "-c" and calls os.system( to execute shell binaries. Attackers commonly use Python's os.system to launch interactive shells (bash, dash, fish, sh, zsh) without dropping a dedicated executable. It relies on process creation telemetry, including the Image path suffix for python/python2/python3 and the command line containing both the Python -c usage and the os.system call with an observed shell path.

Reporting behind it

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Linux Inline Python (-c) Calling os.system to Spawn Shell

Pivot detection · T1059 · 9 related

Changelog

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-inline-python-c-calls-os-system-to-spawn-shell-2d2f44ff

title: Linux Inline Python (-c) Calling os.system to Spawn Shell
id: 3e2f10aa-c1a8-462a-88e4-1d01242c6978
status: test
description: This rule flags Linux process creation where the command line includes inline Python execution via "-c" and calls os.system( to execute shell binaries. Attackers commonly use Python's os.system to launch interactive shells (bash, dash, fish, sh, zsh) without dropping a dedicated executable. It relies on process creation telemetry, including the Image path suffix for python/python2/python3 and the command line containing both the Python -c usage and the os.system call with an observed shell path.
references:
  - https://gtfobins.github.io/gtfobins/python/#shell
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/process_creation/proc_creation_lnx_python_shell_os_system.yml
author: Li Ling, Andy Parkidomo, Robert Rakowski, Blake Hartstein (Bloomberg L.P.), Huntrule Team
date: 2024-09-02
tags:
  - attack.execution
  - attack.t1059
logsource:
  category: process_creation
  product: linux
detection:
  selection_img:
    - Image|endswith:
        - /python
        - /python2
        - /python3
    - Image|contains:
        - /python2.
        - /python3.
  selection_cli:
    CommandLine|contains|all:
      - " -c "
      - os.system(
    CommandLine|contains:
      - /bin/bash
      - /bin/dash
      - /bin/fish
      - /bin/sh
      - /bin/zsh
  condition: all of selection_*
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 2d2f44ff-4611-4778-a8fc-323a0e9850cc
    type: derived

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