Sub-technique of T1546 Event Triggered Execution.View 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. 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.
Rules on DetectionCode tagged with T1546.001.
| Rule | Level | Log source |
|---|---|---|
| Change Default File Association To Executable Via Assoc | high | windows / process_creation |
| Shell Open Registry Keys Manipulation | high | windows / registry_event |
| Registry Modification of MS-settings Protocol Handler | medium | windows / process_creation |
| Suspicious Shell Open Command Registry Modification | medium | windows / registry_set |
| Change Default File Association Via Assoc | low | windows / process_creation |
| Rule | Type | Risk | Data source |
|---|---|---|---|
| Change Default File Association | TTP | NULL | Sysmon EventID 12, Sysmon EventID 13 |
| Suspicious Changes to File Associations | TTP | NULL | Sysmon EventID 1 |
| Windows Change Default File Association For No File Ext | TTP | NULL | Sysmon EventID 1, Windows Event Log Security 4688, CrowdStrike ProcessRollup2 |
| Windows Change File Association Command To Notepad | TTP | NULL | Sysmon EventID 1, Windows Event Log Security 4688, CrowdStrike ProcessRollup2 |
| Windows New Default File Association Value Set | Hunting | NULL | Sysmon EventID 13 |
None recorded.
| Used by | Procedure example |
|---|---|
| GroupKimsuky | Kimsuky has a HWP document stealer module which changes the default program association in the registry to open HWP documents. |
| Used by | Procedure example |
|---|---|
| ToolSILENTTRINITY | SILENTTRINITY can conduct an image hijack of an `.msc` file extension as part of its UAC bypass process. |
Data from MITRE ATT&CK® (Enterprise). ATT&CK® is a registered trademark of The MITRE Corporation.
