JScript Compiler Execution — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: low. Source dates: 2022-05-02 / 2024-04-24.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 07552b3fa5fcdf4f413eee2716e21e9b2cbdf11e733597ca6adbf94645fc70d7

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: JScript Compiler Execution
id: 52788a70-f1da-40dd-8fbd-73b5865d6568
status: test
description: |
    Detects the execution of the "jsc.exe" (JScript Compiler).
    Attacker might abuse this in order to compile JScript files on the fly and bypassing application whitelisting.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Jsc/
    - https://www.phpied.com/make-your-javascript-a-windows-exe/
    - https://twitter.com/DissectMalware/status/998797808907046913
author: frack113
date: 2022-05-02
modified: 2024-04-24
tags:
    - attack.execution
    - attack.stealth
    - attack.t1127
logsource:
    product: windows
    category: process_creation
detection:
    selection:
        - Image|endswith: '\jsc.exe'
        - OriginalFileName: 'jsc.exe'
    condition: selection
falsepositives:
    - Legitimate use to compile JScript by developers.
# Note: Can be decreased to informational or increased to medium depending on how this utility is used.
level: low

Original YAML and metadata in JSON

False positives

• Legitimate use to compile JScript by developers.

Source references

• https://lolbas-project.github.io/lolbas/Binaries/Jsc/
• https://www.phpied.com/make-your-javascript-a-windows-exe/
• https://twitter.com/DissectMalware/status/998797808907046913