Linux Base64 Encoded Pipe to Shell — Sigma Rule

Rule metadata and linked tags

Author: pH-T (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-07-26 / 2023-06-16.

{
  "product": "linux",
  "category": "process_creation"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: db0b1d5baeeaf03db7f79595ab28cf3db17f1b50a083af8f37b2595a498a18b4

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Linux Base64 Encoded Pipe to Shell
id: ba592c6d-6888-43c3-b8c6-689b8fe47337
status: test
description: Detects suspicious process command line that uses base64 encoded input for execution with a shell
references:
    - https://github.com/arget13/DDexec
    - https://www.mandiant.com/resources/blog/barracuda-esg-exploited-globally
author: pH-T (Nextron Systems)
date: 2022-07-26
modified: 2023-06-16
tags:
    - attack.stealth
    - attack.t1140
logsource:
    product: linux
    category: process_creation
detection:
    selection_base64:
        CommandLine|contains: 'base64 '
    selection_exec:
        - CommandLine|contains:
              - '| bash '
              - '| sh '
              - '|bash '
              - '|sh '
        - CommandLine|endswith:
              - ' |sh'
              - '| bash'
              - '| sh'
              - '|bash'
    condition: all of selection_*
falsepositives:
    - Legitimate administration activities
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate administration activities

Source references

• https://github.com/arget13/DDexec
• https://www.mandiant.com/resources/blog/barracuda-esg-exploited-globally