> For the complete documentation index, see [llms.txt](https://cortex-docs.paloaltonetworks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cortex-docs.paloaltonetworks.com/analytics-alerts/alerts-by-name/a-lightweight-javascript-runtime-executing-a-script-wrote-a-python-file-to-disk.md).

# A lightweight JavaScript runtime executing a script wrote a Python file to disk

### Synopsis

| Field                | Value                                                                                                                                                     |
| -------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Activation Period    | 14 Days                                                                                                                                                   |
| Training Period      | 30 Days                                                                                                                                                   |
| Test Period          | N/A (single event)                                                                                                                                        |
| Deduplication Period | 1 Day                                                                                                                                                     |
| Required Data        | XDR Agent with eXtended Threat Hunting (XTH)                                                                                                              |
| ATT\&CK Tactic       | Persistence (TA0003), Execution (TA0002)                                                                                                                  |
| ATT\&CK Technique    | Create or Modify System Process (T1543), Command and Scripting Interpreter: Python (T1059.006), Command and Scripting Interpreter: JavaScript (T1059.007) |
| Severity             | Low                                                                                                                                                       |

### Description

A lightweight JavaScript runtime (Bun or Deno) executing a .js file wrote a Python file to disk.

### Attacker's Goals

Deploy a Python daemon to disk to maintain persistence on the compromised host.

### Investigative actions

* Determine whether it is legitimate for this JavaScript runtime to write Python files on the host.
* Analyze the executed .js file and the written Python file for malicious content.
* Check whether the written Python file was subsequently executed or registered for persistence.
* Review the npm package/command line that invoked the JavaScript runtime for supply-chain compromise.


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