File Explorer Folder Opened Using Explorer Folder Shortcut Via Shell

Status: test
Severity: high
Log source: category process_creation, product windows
Author: @Kostastsale
Source: github.com/SigmaHQ/sigma

Detects the initial execution of "cmd.exe" which spawns "explorer.exe" with the appropriate command line arguments for opening the "My Computer" folder.

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1135` Network Share Discovery

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: File Explorer Folder Opened Using Explorer Folder Shortcut Via Shell
id: c3d76afc-93df-461e-8e67-9b2bad3f2ac4
status: test
description: |
    Detects the initial execution of "cmd.exe" which spawns "explorer.exe" with the appropriate command line arguments for opening the "My Computer" folder.
author: '@Kostastsale'
references:
    - https://ss64.com/nt/shell.html
date: 2022-12-22
modified: 2024-08-23
tags:
    - attack.discovery
    - attack.t1135
logsource:
    product: windows
    category: process_creation
detection:
    selection:
        ParentImage|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
            - '\pwsh.exe'
        Image|endswith: '\explorer.exe'
        CommandLine|contains: 'shell:mycomputerfolder'
    condition: selection
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_explorer_folder_shortcut_via_shell_binary/info.yml

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    ParentImage|endswith:
        - '\cmd.exe'
        - '\powershell.exe'
        - '\pwsh.exe'
    Image|endswith: '\explorer.exe'
    CommandLine|contains: 'shell:mycomputerfolder'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`shell:mycomputerfolder`	`field:"CommandLine" kind:match value:"shell:mycomputerfolder"`
`Image`	ends_with	`\explorer.exe` corpus 13 (sigma 13)	`field:"Image" kind:ends_with value:"\explorer.exe"`
`ParentImage`	ends_with	`\cmd.exe` corpus 20 (sigma 20) `\powershell.exe` corpus 24 (sigma 24) `\pwsh.exe` corpus 21 (sigma 21)	`field:"ParentImage" kind:ends_with`