Techniques › T1546 › T1546.001
T1546.001 Change Default File Association
privilege escalation · persistence — Windows · attack.mitre.org · JSON
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MITRE detection strategy
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analytics
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Sigma rules tagged attack.t1546.001
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KEV CVEs mapped here
<p>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. 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.</p><p>System file associations are listed under <code>HKEY_CLASSES_ROOT\.[extension]</code>, for example <code>HKEY_CLASSES_ROOT\.txt</code>. The entries point to a handler for that extension located at <code>HKEY_CLASSES_ROOT\\[handler]</code>. The various commands are then listed as subkeys underneath the shell key at <code>HKEY_CLASSES_ROOT\\[handler]\shell\\[action]\command</code>. For example:</p>
- <li><code>HKEY_CLASSES_ROOT\txtfile\shell\open\command</code></li><li><code>HKEY_CLASSES_ROOT\txtfile\shell\print\command</code></li><li><code>HKEY_CLASSES_ROOT\txtfile\shell\printto\command</code></li>
KEV CVEs mapped to this technique · CTID Mappings Explorer
None. No KEV entry in the public mapping names this technique. Given that 74.7% of KEV has no mapping at all, this says more about the mapping than about the technique.
Detection strategy · ATT&CK Enterprise v19.2
- DET0061 Detect Default File Association Hijack via Registry & Execution Correlation on Windows v1.0
AN0170 WindowsDetects modification of registry keys used for default file handlers, followed by anomalous process execution from user-initiated file opens. This includes tracking changes under HKCU and HKCR for file extension mappings, and correlating them with new or suspicious handler paths launching unusual child processes (e.g., PowerShell, cmd, wscript).Tunable:
TimeWindowUserContextSuspiciousHandlerPathRegex
Sigma rules · SigmaHQ da9bb07d64, tag attack.t1546.001
Author: Christian Burkard (Nextron Systems)
· 2021-08-30 (modified 2022-01-13) · logsource: product=windows category=registry_event · 152f3630-77c1-4284-bcc0-4cc68ab2f6e7
Detects the shell open key manipulation (exefile and ms-settings) used for persistence and the pattern of UAC Bypass using fodhelper.exe, computerdefaults.exe, slui.exe via registry keys (e.g. UACMe 33 or 62)
Author: Timur Zinniatullin, oscd.community
· 2019-10-21 (modified 2023-03-06) · logsource: product=windows category=process_creation · 3d3aa6cd-6272-44d6-8afc-7e88dfef7061
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.
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
· 2026-01-24 · logsource: product=windows category=registry_set · 9e8894c0-0ae0-11ef-9d85-1f2942bec57c
Detects modifications to shell open registry keys that point to suspicious locations typically used by malware for persistence.
Generally, modifications to the `*\shell\open\command` registry key can indicate an attempt to change the default action for opening files,
and various UAC bypass or persistence techniques involve modifying these keys to execute malicious scripts or binaries.
Author: Nasreddine Bencherchali (Nextron Systems)
· 2022-06-28 (modified 2023-03-06) · logsource: product=windows category=process_creation · ae6f14e6-14de-45b0-9f44-c0986f50dc89
Detects when a program changes the default file association of any extension to an executable.
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.
Author: frack113, Swachchhanda Shrawan Poudel (Nextron Systems)
· 2021-12-20 (modified 2026-01-24) · logsource: product=windows category=process_creation · dd3ee8cc-f751-41c9-ba53-5a32ed47e563
Detects registry modifications to the 'ms-settings' protocol handler, which is frequently targeted for UAC bypass or persistence.
Attackers can modify this registry to execute malicious code with elevated privileges by hijacking the command execution path.
Rules tagged at the parent level (attack.t1546) 10
These target the parent technique, not this sub-technique specifically. Listed for completeness, not counted as coverage.
Author: Omkar Gudhate
· 2020-09-27 (modified 2023-09-28) · logsource: product=windows category=registry_set · 07743f65-7ec9-404a-a519-913db7118a8d
Detects changes to 'HKCU\Software\Classes\Folder\shell\open\command\DelegateExecute'
Author: Kyaw Min Thein, Furkan Caliskan (@caliskanfurkan_)
· 2020-06-22 (modified 2023-10-11) · logsource: product=windows category=process_creation · 0ba863e6-def5-4e50-9cea-4dd8c7dc46a4
Detects the malicious use of a control panel item
Author: frack113
· 2022-04-23 · logsource: product=windows category=file_event · 0c3fac91-5627-46e8-a6a8-a0d7b9b8ae1b
Get-Variable is a valid PowerShell cmdlet
WindowsApps is by default in the path where PowerShell is executed.
So when the Get-Variable command is issued on PowerShell execution, the system first looks for the Get-Variable executable in the path and executes the malicious binary instead of looking for the PowerShell cmdlet.
Author: Nasreddine Bencherchali (Nextron Systems)
· 2023-02-08 · logsource: product=windows category=file_event · 117d3d3a-755c-4a61-b23e-9171146d094c
Detects the creation of a macro file for Outlook.
Author: Nasreddine Bencherchali (Nextron Systems)
· 2021-04-05 (modified 2023-08-17) · logsource: product=windows category=registry_set · 396ae3eb-4174-4b9b-880e-dc0364d78a19
Detects the modification of Outlook setting "LoadMacroProviderOnBoot" which if enabled allows the automatic loading of any configured VBA project/module
Author: Denis Szadkowski, DIRT / DCSO CyTec
· 2022-10-09 · logsource: product=windows service=application · 711ab2fe-c9ba-4746-8840-5228a58c3cb8
This rule detects the execution of the extended storage procedure backdoor named Maggie in the context of Microsoft SQL server
Author: MSTIC, FPT.EagleEye
· 2021-06-15 (modified 2022-10-09) · logsource: product=windows category=process_creation · 7ba08e95-1e0b-40cd-9db5-b980555e42fd
Suspicious behaviours related to an actor tracked by Microsoft as SOURGUM
Author: @ScoubiMtl
· 2021-04-05 (modified 2023-02-08) · logsource: product=windows category=file_event · 8c31f563-f9a7-450c-bfa8-35f8f32f1f61
Detects the creation of a macro file for Outlook.
Author: Florian Roth (Nextron Systems)
· 2021-03-09 (modified 2023-03-09) · logsource: product=windows category=process_creation · bbb2dedd-a0e3-46ab-ba6c-6c82ae7a9aa7
Detects activity observed by different researchers to be HAFNIUM group activity (or related) on Exchange servers
Author: @ScoubiMtl
· 2021-04-05 (modified 2023-08-17) · logsource: product=windows category=registry_set · e3b50fa5-3c3f-444e-937b-0a99d33731cd
Detects the modification of Outlook security setting to allow unprompted execution of macros.