
title: Change Default File Association
author: Timur Zinniatullin, oscd.community
date: 2019/10/21
description: 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.
detection:
  SELECTION_1:
    EventID: 1
  SELECTION_2:
    CommandLine: '*cmd*'
  SELECTION_3:
    CommandLine: '*/c*'
  SELECTION_4:
    CommandLine: '*assoc*'
  condition: (SELECTION_1 and SELECTION_2 and SELECTION_3 and SELECTION_4)
falsepositives:
- Admin activity
fields:
- Image
- CommandLine
- User
- LogonGuid
- Hashes
- ParentProcessGuid
- ParentCommandLine
id: 3d3aa6cd-6272-44d6-8afc-7e88dfef7061
level: low
logsource:
  category: process_creation
  product: windows
modified: 2019/11/04
references:
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1546.001/T1546.001.md
status: experimental
tags:
- attack.persistence
- attack.t1546.001
- attack.t1042
ruletype: SIGMA
