Shellshock Expression

SIGMA detection rule by Florian Roth (Nextron Systems) · NOASSERTION

Detects shellshock expressions in log files

title: Shellshock Expression
id: c67e0c98-4d39-46ee-8f6b-437ebf6b950e
status: test
description: Detects shellshock expressions in log files
references:
    - https://owasp.org/www-pdf-archive/Shellshock_-_Tudor_Enache.pdf
author: Florian Roth (Nextron Systems)
date: 2017-03-14
modified: 2022-10-09
tags:
    - attack.persistence
    - attack.t1505.003
logsource:
    product: linux
detection:
    keywords:
        - '(){:;};'
        - '() {:;};'
        - '() { :;};'
        - '() { :; };'
    condition: keywords
falsepositives:
    - Unknown
level: high

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

9bb04070-ae4f-4f74-a8df-dec041122f07

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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