Analysis of a JSE File (Kimsuky APT)
2026-02-03 • Shubho57 •
https://medium.com/@shubhandrew/analysis-of-a-jse-file-kimsuky-apt-79588d103f73
The analyzed Kimsuky-linked JSE file acts as a multi-stage Windows script dropper that embeds a twice-base64-decoded PE executable and writes it to disk for execution. The script abuses Windows Script Host components including FileSystemObject, ADODB Stream, XML DOM base64 handling, and hidden PowerShell execution to decode, drop, and run payload files from locations such as ProgramData or temporary directories. Static analysis of the stage-two executable shows native Win32 code using WinHTTP APIs for HTTP or HTTPS beaconing, with no plaintext C2 visible, suggesting an encoded or dynamically assembled configuration. Reported behaviors also include self-path discovery, special-folder access, file deletion activity, and an assessment that the payload likely functions as an info-stealer loader. The excerpt ties the activity to Kimsuky and highlights common defensive concerns around script-host abuse, hidden PowerShell, and obfuscated loader configuration.
Indicators of Compromise
| Type | Value | First Seen | Last Seen |
|---|---|---|---|
| YARA | KIMSUKY_Dropper_Archive | 2026-02-03 | 2026-02-03 |
| YARA | KIMSUKY_NUKESPED_DLL_Payload | 2026-02-03 | 2026-02-03 |
| YARA | KIMSUKY_NUKESPED_JSE_Loader | 2026-02-03 | 2026-02-03 |
| HASH | 485a886acdf832cce3fb902483e30f6… | 2026-02-03 | 2026-02-03 |
| HASH | c89af74145a6dd5d6ee0f8283ae9420… | 2026-02-03 | 2026-02-03 |
| HASH | 81e384471fcfa6752cb81ca1b7b9ee4… | 2026-02-03 | 2026-02-03 |
| HASH | 7d994b591c2d4fafeb3e71278229566e | 2025-11-06 | 2026-02-03 |