Detection rules › Sigma

Unix Shell Configuration Modification

Status
test
Severity
medium
Log source
product linux, service auditd
Author
Peter Matkovski, IAI
Source
github.com/SigmaHQ/sigma

Detect unix shell configuration modification. Adversaries may establish persistence through executing malicious commands triggered when a new shell is opened.

MITRE ATT&CK coverage

Event coverage

Rule body yaml

title: Unix Shell Configuration Modification
id: a94cdd87-6c54-4678-a6cc-2814ffe5a13d
related:
    - id: e74e15cc-c4b6-4c80-b7eb-dfe49feb7fe9
      type: obsolete
status: test
description: Detect unix shell configuration modification. Adversaries may establish persistence through executing malicious commands triggered when a new shell is opened.
references:
    - https://objective-see.org/blog/blog_0x68.html
    - https://web.archive.org/web/20221204161143/https://www.glitch-cat.com/p/green-lambert-and-attack
    - https://www.anomali.com/blog/pulling-linux-rabbit-rabbot-malware-out-of-a-hat
author: Peter Matkovski, IAI
date: 2023-03-06
modified: 2023-03-15
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1546.004
logsource:
    product: linux
    service: auditd
detection:
    selection:
        type: 'PATH'
        name:
            - '/etc/shells'
            - '/etc/profile'
            - '/etc/profile.d/*'
            - '/etc/bash.bashrc'
            - '/etc/bashrc'
            - '/etc/zsh/zprofile'
            - '/etc/zsh/zshrc'
            - '/etc/zsh/zlogin'
            - '/etc/zsh/zlogout'
            - '/etc/csh.cshrc'
            - '/etc/csh.login'
            - '/root/.bashrc'
            - '/root/.bash_profile'
            - '/root/.profile'
            - '/root/.zshrc'
            - '/root/.zprofile'
            - '/home/*/.bashrc'
            - '/home/*/.zshrc'
            - '/home/*/.bash_profile'
            - '/home/*/.zprofile'
            - '/home/*/.profile'
            - '/home/*/.bash_login'
            - '/home/*/.bash_logout'
            - '/home/*/.zlogin'
            - '/home/*/.zlogout'
    condition: selection
falsepositives:
    - Admin or User activity are expected to generate some false positives
level: medium

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    type: 'PATH'
    name:
        - '/etc/shells'
        - '/etc/profile'
        - '/etc/profile.d/*'
        - '/etc/bash.bashrc'
        - '/etc/bashrc'
        - '/etc/zsh/zprofile'
        - '/etc/zsh/zshrc'
        - '/etc/zsh/zlogin'
        - '/etc/zsh/zlogout'
        - '/etc/csh.cshrc'
        - '/etc/csh.login'
        - '/root/.bashrc'
        - '/root/.bash_profile'
        - '/root/.profile'
        - '/root/.zshrc'
        - '/root/.zprofile'
        - '/home/*/.bashrc'
        - '/home/*/.zshrc'
        - '/home/*/.bash_profile'
        - '/home/*/.zprofile'
        - '/home/*/.profile'
        - '/home/*/.bash_login'
        - '/home/*/.bash_logout'
        - '/home/*/.zlogin'
        - '/home/*/.zlogout'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
nameeq
  • /etc/bash.bashrc
  • /etc/bashrc
  • /etc/csh.cshrc
  • /etc/csh.login
  • /etc/profile
  • /etc/profile.d/*
  • /etc/shells
  • /etc/zsh/zlogin
  • /etc/zsh/zlogout
  • /etc/zsh/zprofile
  • /etc/zsh/zshrc
  • /home/*/.bash_login
  • /home/*/.bash_logout
  • /home/*/.bash_profile
  • /home/*/.bashrc
  • /home/*/.profile
  • /home/*/.zlogin
  • /home/*/.zlogout
  • /home/*/.zprofile
  • /home/*/.zshrc
  • /root/.bash_profile
  • /root/.bashrc
  • /root/.profile
  • /root/.zprofile
  • /root/.zshrc
typeeq
  • PATH