Shell Invocation via Env Command - Linux

Status: test
Severity: high
Log source: category process_creation, product linux
Author: Li Ling, Andy Parkidomo, Robert Rakowski, Blake Hartstein (Bloomberg L.P.)
Source: github.com/SigmaHQ/sigma

Detects the use of the env command to invoke a shell. This may indicate an attempt to bypass restricted environments, escalate privileges, or execute arbitrary commands.

Known false positives

Github operations such as ghe-backup

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.004` Command and Scripting Interpreter: Unix Shell

Telemetry coverage

Platform	Record / event type
Linux	Event ID 1: Process Create

Rule body

title: Shell Invocation via Env Command - Linux
id: bed978f8-7f3a-432b-82c5-9286a9b3031a
status: test
description: |
    Detects the use of the env command to invoke a shell. This may indicate an attempt to bypass restricted environments, escalate privileges, or execute arbitrary commands.
references:
    - https://gtfobins.github.io/gtfobins/env/#shell
    - https://www.elastic.co/guide/en/security/current/linux-restricted-shell-breakout-via-linux-binary-s.html
author: Li Ling, Andy Parkidomo, Robert Rakowski, Blake Hartstein (Bloomberg L.P.)
date: 2024-09-02
modified: 2026-01-08
tags:
    - attack.execution
    - attack.t1059.004
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/env'
        CommandLine|contains:
            - '/bin/bash'
            - '/bin/dash'
            - '/bin/fish'
            - '/bin/sh'
            - '/bin/zsh'
    condition: selection
falsepositives:
    - Github operations such as ghe-backup
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '/env'
    CommandLine|contains:
        - '/bin/bash'
        - '/bin/dash'
        - '/bin/fish'
        - '/bin/sh'
        - '/bin/zsh'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`/bin/bash` `/bin/dash` `/bin/fish` `/bin/sh` `/bin/zsh`	`field:"CommandLine" kind:match`
`Image`	ends_with	`/env`	`field:"Image" kind:ends_with value:"/env"`