Suspicious Chromium Browser Instance Executed With Custom Extension — Sigma Rule

Rule metadata and linked tags

Author: Aedan Russell, frack113, X__Junior (Nextron Systems). Source status: test; severity: high. Source dates: 2022-06-19 / 2023-11-28.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 758b9cd124b80edafa45ea4c84d405bb3f42a5d5a50cff2371e7ab708f0f938a

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: Suspicious Chromium Browser Instance Executed With Custom Extension
id: 27ba3207-dd30-4812-abbf-5d20c57d474e
related:
    - id: 88d6e60c-759d-4ac1-a447-c0f1466c2d21
      type: similar
status: test
description: Detects a suspicious process spawning a Chromium based browser process with the 'load-extension' flag to start an instance with a custom extension
references:
    - https://redcanary.com/blog/chromeloader/
    - https://emkc.org/s/RJjuLa
    - https://www.mandiant.com/resources/blog/lnk-between-browsers
author: Aedan Russell, frack113, X__Junior (Nextron Systems)
date: 2022-06-19
modified: 2023-11-28
tags:
    - attack.persistence
    - attack.t1176.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith:
            - '\cmd.exe'
            - '\cscript.exe'
            - '\mshta.exe'
            - '\powershell.exe'
            - '\pwsh.exe'
            - '\regsvr32.exe'
            - '\rundll32.exe'
            - '\wscript.exe'
        Image|endswith:
            - '\brave.exe'
            - '\chrome.exe'
            - '\msedge.exe'
            - '\opera.exe'
            - '\vivaldi.exe'
        CommandLine|contains: '--load-extension='
    condition: selection
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_browsers_chromium_susp_load_extension/info.yml

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://redcanary.com/blog/chromeloader/
• https://emkc.org/s/RJjuLa
• https://www.mandiant.com/resources/blog/lnk-between-browsers