Sigma

Example Rule

title: File or Folder Permissions Change
id: 74c01ace-0152-4094-8ae2-6fd776dd43e5
status: test
description: Detects file and folder permission changes.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1222.002/T1222.002.md
author: Jakob Weinzettl, oscd.community
date: 2019/09/23
modified: 2021/11/27
tags:
    - attack.defense_evasion
    - attack.t1222.002
logsource:
    product: linux
    service: auditd
detection:
    selection:
        type: 'EXECVE'
        a0|contains:
            - 'chmod'
            - 'chown'
    condition: selection
falsepositives:
    - User interacting with files permissions (normal/daily behaviour).
level: low

Convert Rules to Splunk

# install tools
pip3 install sigmatools

# convert rule
sigmac -t splunk -c splunk-windows rules/windows/sysmon/sysmon_susp_image_load.yml

Custom Field Mapping

• mapping fields

...
fieldmappings:
  EventID: EventCode

source

• Sigma github Repo
• Sigma2SplunkAlert Tutorial
• unicoder: web converter
• Sigma wiki