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Trojan.JS.EMANSREPO.A

September 18, 2024
 Analysis by: John Rainier Navato
 ALIASES:

Trojan:JS/MalScript!MSR (MICROSOFT)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

13,237 bytes

File Type:

JS

Memory Resident:

No

Initial Samples Received Date:

11 Sep 2024

Payload:

Connects to URLs/IPs

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Trojan adds the following processes:

  • powershell -NoProfile -WindowStyle Hidden -ExecutionPolicy Bypass -File "%User Temp%\script.ps1"

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}.{BLOCKED}.{BLOCKED}.185/script.ps1

It saves the files it downloads using the following names:

As of this writing, the said sites are inaccessible.

Other Details

This Trojan does the following:

  • It checks if %User Temp%\script.ps1 exists.
    • If not, it connects to http://{BLCOKED}.{BLOCKED}.{BLOCKED}.185/script.ps1 to download a malicious script, save it as %User Temp%\script.ps1, and execute it.
    • If it exists, it terminates itself

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

19.584.05

FIRST VSAPI PATTERN DATE:

11 Sep 2024

VSAPI OPR PATTERN File:

19.585.00

VSAPI OPR PATTERN Date:

12 Sep 2024

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

    • Downloader.JS.TRX.XXJSE9EFF062

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 4

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\script.ps1

Step 5

Scan your computer with your Trend Micro product to delete files detected as Trojan.JS.EMANSREPO.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check the following Trend Micro Support pages for more information:


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