Detection rules › Sigma
Change Default File Association Via Assoc
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.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1546.001 Event Triggered Execution: Change Default File Association |
| Privilege Escalation | T1546.001 Event Triggered Execution: Change Default File Association |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
Rule body yaml
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
Stages and Predicates
Stage 0: condition
all of selection_*Stage 1: selection_img
selection_img:
- Image|endswith: '\cmd.exe'
- OriginalFileName: 'Cmd.Exe'
Stage 2: selection_cli
selection_cli:
CommandLine|contains: 'assoc'
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.
| Field | Kind | Values |
|---|---|---|
CommandLine | match |
|
Image | ends_with |
|
OriginalFileName | eq |
|