Change Default File Association Via Assoc — Sigma Rule

Rule metadata and linked tags

Author: Timur Zinniatullin, oscd.community. Source status: test; severity: low. Source dates: 2019-10-21 / 2023-03-06.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 5fcbb55bc7f8f3af2f6af638cc3ca0cc710a638a2e643c3493e2e9e48bc0e5ba

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: Change Default File Association Via Assoc
id: 3d3aa6cd-6272-44d6-8afc-7e88dfef7061
related:
    - id: ae6f14e6-14de-45b0-9f44-c0986f50dc89
      type: similar
status: test
description: |
    Detects file association changes using the builtin "assoc" command.
    When a file is opened, the default program used to open the file (also called the file association or handler) is checked. File association selections are stored in the Windows Registry and can be edited by users, administrators, or programs that have Registry access or by administrators using the built-in assoc utility. Applications can modify the file association for a given file extension to call an arbitrary program when a file with the given extension is opened.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1546.001/T1546.001.md
author: Timur Zinniatullin, oscd.community
date: 2019-10-21
modified: 2023-03-06
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1546.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\cmd.exe'
        - OriginalFileName: 'Cmd.Exe'
    selection_cli:
        CommandLine|contains: 'assoc'
    condition: all of selection_*
falsepositives:
    - Admin activity
level: low
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_cmd_assoc_execution/info.yml

Original YAML and metadata in JSON

False positives

• Admin activity

Source references

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1546.001/T1546.001.md