T1546.001: Event Triggered Execution: Change Default File Association

Framework: MITRE ATT&CK · Tactic: Persistence · Total Cataloged Families: 3 · Observed Samples: 17 · Primary Threat Categories: Advanced Threat · Trojan

Operational Executive Summary

T1546.001 (Event Triggered Execution: Change Default File Association) is classified under the Persistence tactic within the MITRE ATT&CK framework. Mechanisms that adversaries use to maintain access across reboots, credential changes, and system maintenance, including Registry Run keys, scheduled tasks, and autostart services. In telemetry gathered across enterprise endpoints and the EMBER 2018 benchmark, this technique was weaponized across 3 distinct malware families, totaling over 17 validated samples.

Technical Anatomy & Adversary Tradecraft

Adversaries leverage Event Triggered Execution: Change Default File Association to accomplish operational objectives while minimizing anomalous forensic footprints. When executing Event Triggered Execution: Change Default File Association, malicious binaries commonly interact directly with low-level Windows APIs, kernel mode drivers, or native scripting interfaces to bypass traditional file-integrity monitors and static antivirus signatures.

In modern multi-stage campaigns, T1546.001 is frequently observed functioning as an intermediate bridge: initial access payloads (such as spearphishing loaders or exploit macros) execute Event Triggered Execution: Change Default File Association to establish in-memory execution or persistence before staging secondary ransomware or data-exfiltration implants.

Authoritative MITRE ATT&CK Reference: View official technique documentation, sub-techniques, and adversary groups at https://attack.mitre.org/techniques/T1546/001/.

Detection Engineering & Threat Hunting

Detecting Event Triggered Execution: Change Default File Association requires telemetry correlation across endpoint detection and response (EDR) agents, Sysmon event streams, and security information event management (SIEM) pipelines:

Process Creation & Lineage: Monitor parent-child process anomalies where unexpected parent binaries (e.g., Office executables, web browsers, or script hosts) spawn command shells or native Windows utilities.
API Hooking & Behavioral Telemetry: EDR platforms should flag rapid calls to memory allocation, process injection, or registry manipulation APIs originating from unbacked executable memory regions.
Network Anomaly Correlation: Cross-reference endpoint execution timestamps with external network socket establishment to identify anomalous beaconing or covert data staging.

SOC Containment & Hardening Guidance

To mitigate risks associated with T1546.001 (Event Triggered Execution: Change Default File Association) across production infrastructure, security teams should implement the following defensive controls:

Attack Surface Reduction (ASR): Enforce strict application control policies (WDAC or AppLocker) to restrict execution to signed and verified corporate binaries.
Least Privilege & Credential Hygiene: Restrict local administrative privileges to prevent adversaries from tampering with defensive agents or escalating privileges.
Network Microsegmentation: Restrict lateral communication across endpoint VLANs to prevent wormable payloads from utilizing Event Triggered Execution: Change Default File Association across adjacent network segments.

→ Incident Response Guidance: Read our Active Incident Response Playbook

Cataloged Malware Families Utilizing T1546.001 (3 Families)

The following malware families in the SystemHelpDesk catalog have been verified utilizing T1546.001 (Event Triggered Execution: Change Default File Association):

3 families

Family	Category	Sample Count	Technical Summary
kingsoft	Advanced Threat	`8`	PUA:Win32/Kingsoft (often associated with Kingsoft Antivirus or WPS Office) refers to software from the Chinese software developer Kingsoft that is freq...
winreg	Trojan	`8`	Trojan:Win32/Winreg (often categorized generically as a Registry Modifier) is a classification for malware whose primary defining characteristic is the aggr...
webaltatoolbar	Advanced Threat	`1`	Adware:Win32/Webaltatoolbar is a historically notorious Potentially Unwanted Program (PUP) and browser hijacker (`T1176`). Originating in Russia, Webalta aggres...