Local System Accounts Discovery - Linux — Sigma Rule

Rule metadata and linked tags

Author: Alejandro Ortuno, oscd.community, CheraghiMilad. Source status: test; severity: low. Source dates: 2020-10-08 / 2024-12-10.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 2288be23b4893e92496d29b07610a99b4cd186ef87849186ed30a9b17b3422d5

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: Local System Accounts Discovery - Linux
id: b45e3d6f-42c6-47d8-a478-df6bd6cf534c
status: test
description: Detects enumeration of local system accounts. This information can help adversaries determine which local accounts exist on a system to aid in follow-on behavior.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1087.001/T1087.001.md
    - https://my.f5.com/manage/s/article/K589
    - https://man.freebsd.org/cgi/man.cgi?pwd_mkdb
author: Alejandro Ortuno, oscd.community, CheraghiMilad
date: 2020-10-08
modified: 2024-12-10
tags:
    - attack.discovery
    - attack.t1087.001
logsource:
    category: process_creation
    product: linux
detection:
    selection_1:
        Image|endswith: '/lastlog'
    selection_2:
        CommandLine|contains: '''x:0:'''
    selection_3:
        Image|endswith:
            - '/cat'
            - '/ed'
            - '/head'
            - '/more'
            - '/nano'
            - '/tail'
            - '/vi'
            - '/vim'
            - '/less'
            - '/emacs'
            - '/sqlite3'
            - '/makemap'
        CommandLine|contains:
            - '/etc/passwd'
            - '/etc/shadow'
            - '/etc/sudoers'
            - '/etc/spwd.db'
            - '/etc/pwd.db'
            - '/etc/master.passwd'
    selection_4:
        Image|endswith: '/id'
    selection_5:
        Image|endswith: '/lsof'
        CommandLine|contains: '-u'
    condition: 1 of selection*
falsepositives:
    - Legitimate administration activities
level: low

Original YAML and metadata in JSON

False positives

• Legitimate administration activities

Source references

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1087.001/T1087.001.md
• https://my.f5.com/manage/s/article/K589
• https://man.freebsd.org/cgi/man.cgi?pwd_mkdb