Change Default File Association Via Assoc

SIGMA detection rule by Timur Zinniatullin, oscd.community · NOASSERTION

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.

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

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