Renamed VsCode Code Tunnel Execution - File Indicator

Status: test
Severity: high
Log source: category file_event, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the creation of a file with the name "code_tunnel.json" which indicate execution and usage of VsCode tunneling utility by an "Image" or "Process" other than VsCode.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	No specific technique

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 11: FileCreate

Rule body

title: Renamed VsCode Code Tunnel Execution - File Indicator
id: d102b8f5-61dc-4e68-bd83-9a3187c67377
status: test
description: |
    Detects the creation of a file with the name "code_tunnel.json" which indicate execution and usage of VsCode tunneling utility by an "Image" or "Process" other than VsCode.
references:
    - https://ipfyx.fr/post/visual-studio-code-tunnel/
    - https://badoption.eu/blog/2023/01/31/code_c2.html
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-10-25
tags:
    - attack.command-and-control
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith: '\code_tunnel.json'
    filter_main_legit_name:
        # Note: There might be other legitimate names for VsCode. Please add them if found
        Image|endswith:
            - '\code-tunnel.exe'
            - '\code.exe'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    TargetFilename|endswith: '\code_tunnel.json'

Stage 2: `not filter_main_legit_name`

filter_main_legit_name:
    Image|endswith:
        - '\code-tunnel.exe'
        - '\code.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	ends_with	`\code-tunnel.exe`	`excludes:Image` `field:"Image" value:"\code-tunnel.exe"`
`Image`	ends_with	`\code.exe`	`excludes:Image` `field:"Image" value:"\code.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`TargetFilename`	ends_with	`\code_tunnel.json` corpus 2 (sigma 2)	`field:"TargetFilename" kind:ends_with value:"\code_tunnel.json"`