Detection rules › Sigma
Change Default File Association To Executable Via Assoc
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.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1546.001 Event Triggered Execution: Change Default File Association |
| Privilege Escalation | T1546.001 Event Triggered Execution: Change Default File Association |
Event coverage
| Provider | Event ID | Title |
|---|---|---|
| Sysmon | 1 | Process creation |
Stages and Predicates
Stage 1: all of selection_img
or:
Image|endswith: '\cmd.exe'
OriginalFileName: Cmd.Exe
Stage 2: all of selection_cli
CommandLine|contains: 'assoc '
CommandLine|contains: exefile
Stage 3: not filter
CommandLine|contains: '.exe=exefile'
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
CommandLine | match |
|
Image | ends_with |
|
OriginalFileName | eq |
|