Cscript/Wscript Uncommon Script Extension Execution — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: high. Source dates: 2023-05-15 / 2023-06-19.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: e53a18a04b94bd598060bf5e6e53c8f19c210bb1c44bbc8dad1bbe09f96446d8

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Cscript/Wscript Uncommon Script Extension Execution
id: 99b7460d-c9f1-40d7-a316-1f36f61d52ee
status: test
description: Detects Wscript/Cscript executing a file with an uncommon (i.e. non-script) extension
references:
    - Internal Research
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-05-15
modified: 2023-06-19
tags:
    - attack.execution
    - attack.t1059.005
    - attack.t1059.007
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - OriginalFileName:
              - 'wscript.exe'
              - 'cscript.exe'
        - Image|endswith:
              - '\wscript.exe'
              - '\cscript.exe'
    selection_extension:
        CommandLine|contains:
            # Note: add additional potential suspicious extension
            # We could specify the "//E:" flag to avoid typos by admin. But since that's prone to blind spots via the creation of assoc it's better not to include it
            - '.csv'
            - '.dat'
            - '.doc'
            - '.gif'
            - '.jpeg'
            - '.jpg'
            - '.png'
            - '.ppt'
            - '.txt'
            - '.xls'
            - '.xml'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• Internal Research (source note; no public URL supplied)