Sigma rule: Change Default File Association Via Assoc

Rule

Title

Change Default File Association Via Assoc

Status

test

Level

low

Author

Timur Zinniatullin, oscd.community

Date

2019-10-21

Modified

2023-03-06

File

rules/windows/process_creation/proc_creation_win_cmd_assoc_execution.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects file association changes using the builtin "assoc" command.
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.

Log source

product

windows

category

process_creation

Detection

selection_img:
    - Image|endswith: '\cmd.exe'
    - OriginalFileName: 'Cmd.Exe'
selection_cli:
    CommandLine|contains: 'assoc'
condition: all of selection_*

False positives (as the rule lists them)

• Admin activity

Tags

• attack.privilege-escalation
• attack.persistence
• attack.t1546.001

MITRE ATT&CK ids this rule names

• T1546.001

Related rules

• ae6f14e6-14de-45b0-9f44-c0986f50dc89 (similar)

References

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1546.001/T1546.001.md

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_cmd_assoc_execution.yml