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Detection rules › Sigma

Suspicious Chromium Browser Instance Executed With Custom Extension

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Aedan Russell, frack113, X__Junior (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects a suspicious process spawning a Chromium based browser process with the 'load-extension' flag to start an instance with a custom extension

MITRE ATT&CK coverage

TacticTechniques
PersistenceT1176.001 Software Extensions: Browser Extensions

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation
Security-AuditingEvent ID 4688A new process has been created.

Rule body yaml

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

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

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='

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
CommandLinematch
  • --load-extension= corpus 2 (sigma 2)
Imageends_with
  • \brave.exe corpus 11 (sigma 11)
  • \chrome.exe corpus 13 (sigma 13)
  • \msedge.exe corpus 14 (sigma 14)
  • \opera.exe corpus 11 (sigma 11)
  • \vivaldi.exe corpus 11 (sigma 11)
ParentImageends_with
  • \cmd.exe corpus 20 (sigma 20)
  • \cscript.exe corpus 17 (sigma 17)
  • \mshta.exe corpus 13 (sigma 13)
  • \powershell.exe corpus 24 (sigma 24)
  • \pwsh.exe corpus 21 (sigma 21)
  • \regsvr32.exe corpus 11 (sigma 11)
  • \rundll32.exe corpus 15 (sigma 15)
  • \wscript.exe corpus 19 (sigma 19)