T1546.001sub-technique of T1546 Event Triggered Execution

Change Default File Association

Windowsnothing on this site yetT1546.001 on attack.mitre.org

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.
MITRE ATT&CK 19.2, retrieved 2026-09-12

If this is happening now

Checklists and playbooks to open while the alert is still live.

Playbook for this stage

Suspicious execution on an endpoint

An EDR alert, an unexplained process, or a user reporting something odd.

Playbook for this stage

Cloud account compromise

Impossible travel, an unrecognised inbox rule, or a reported invoice-fraud attempt.

how MITRE says to see it

Detect Default File Association Hijack via Registry & Execution Correlation on Windows

Detects 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...

the rest of T1546

T1546.002 Screensaver · not covered yet
T1546.003 Windows Management Instrumentation Event Subscription · 5 on this site
T1546.004 Unix Shell Configuration Modification · not covered yet
T1546.005 Trap · not covered yet
T1546.006 LC_LOAD_DYLIB Addition · not covered yet
T1546.007 Netsh Helper DLL · not covered yet
T1546.008 Accessibility Features · not covered yet
T1546.009 AppCert DLLs · not covered yet
T1546.010 AppInit DLLs · not covered yet
T1546.011 Application Shimming · not covered yet
T1546.012 Image File Execution Options Injection · not covered yet
T1546.013 PowerShell Profile · not covered yet
T1546.014 Emond · not covered yet
T1546.015 Component Object Model Hijacking · not covered yet
T1546.016 Installer Packages · not covered yet
T1546.017 Udev Rules · not covered yet
T1546.018 Python Startup Hooks · not covered yet

The description, detection analytics and mitigations are reproduced from MITRE ATT&CK, version 19.2, under its terms of use. The checklists, hunts, labs and everything else linked here are this site’s.