type: attack-pattern
spec_version: 2.1
id: attack-pattern--98034fef-d9fb-4667-8dc4-2eab6231724c
created: 2020-01-24T13:40:47.282Z
created_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
revoked: no
external_references: source_name: mitre-attack
url: https://attack.mitre.org/techniques/T1546/001
external_id: T1546.001
source_name: Microsoft Change Default Programs
description: Microsoft. (n.d.). Change which programs Windows 7 uses by default. Retrieved July 26, 2016.
url: https://support.microsoft.com/en-us/help/18539/windows-7-change-default-programs
source_name: Microsoft File Handlers
description: Microsoft. (n.d.). Specifying File Handlers for File Name Extensions. Retrieved September 12, 2024.
url: https://learn.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2015/extensibility/specifying-file-handlers-for-file-name-extensions?view=vs-2015
source_name: Microsoft Assoc Oct 2017
description: Plett, C. et al.. (2017, October 15). assoc. Retrieved August 7, 2018.
url: https://docs.microsoft.com/windows-server/administration/windows-commands/assoc
source_name: TrendMicro TROJ-FAKEAV OCT 2012
description: Sioting, S. (2012, October 8). TROJ_FAKEAV.GZD. Retrieved August 8, 2018.
url: https://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/troj_fakeav.gzd
object_marking_refs: marking-definition--fa42a846-8d90-4e51-bc29-71d5b4802168
modified: 2025-10-24T17:49:07.854Z
name: Change Default File Association
description: Adversaries may establish persistence by executing malicious content triggered by a file type association. 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.(Citation: Microsoft Change Default Programs)(Citation: Microsoft File Handlers)(Citation: Microsoft Assoc Oct 2017) 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.

System file associations are listed under HKEY_CLASSES_ROOT\.[extension], for example HKEY_CLASSES_ROOT\.txt. The entries point to a handler for that extension located at HKEY_CLASSES_ROOT\\[handler]. The various commands are then listed as subkeys underneath the shell key at HKEY_CLASSES_ROOT\\[handler]\shell\\[action]\command. For example: 

* HKEY_CLASSES_ROOT\txtfile\shell\open\command
* HKEY_CLASSES_ROOT\txtfile\shell\print\command
* HKEY_CLASSES_ROOT\txtfile\shell\printto\command

The values of the keys listed are commands that are executed when the handler opens the file extension. Adversaries can modify these values to continually execute arbitrary commands.(Citation: TrendMicro TROJ-FAKEAV OCT 2012)
kill_chain_phases: kill_chain_name: mitre-attack
phase_name: privilege-escalation
kill_chain_name: mitre-attack
phase_name: persistence
x_mitre_attack_spec_version: 3.2.0
x_mitre_contributors: Travis Smith, Tripwire
Stefan Kanthak
x_mitre_deprecated: no
x_mitre_domains: enterprise-attack
x_mitre_is_subtechnique: yes
x_mitre_modified_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
x_mitre_platforms: Windows
x_mitre_version: 1.1