Change Default File Association To Executable Via Assoc

 1title: Change Default File Association To Executable Via Assoc
 2id: ae6f14e6-14de-45b0-9f44-c0986f50dc89
 3related:
 4    - id: 3d3aa6cd-6272-44d6-8afc-7e88dfef7061
 5      type: derived
 6status: test
 7description: |
 8    Detects when a program changes the default file association of any extension to an executable.
 9    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.    
10references:
11    - https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/assoc
12author: Nasreddine Bencherchali (Nextron Systems)
13date: 2022-06-28
14modified: 2023-03-06
15tags:
16    - attack.persistence
17    - attack.t1546.001
18logsource:
19    category: process_creation
20    product: windows
21detection:
22    selection_img:
23        - Image|endswith: '\cmd.exe'
24        - OriginalFileName: 'Cmd.Exe'
25    selection_cli:
26        CommandLine|contains|all:
27            - 'assoc '
28            - 'exefile'
29    filter:
30        CommandLine|contains: '.exe=exefile'
31    condition: all of selection_* and not filter
32falsepositives:
33    - Unknown
34level: high