Analysis by: Mar Philip Elaurza
ALIASES:

JS/TrojanDownloader.Nemucod.KR (ESET), JS:Trojan.JS.Downloader.DO (F-Secure)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Via email

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

  TECHNICAL DETAILS

File Size: 3,715 bytes
File Type: JS
Memory Resident: Yes
Initial Samples Received Date: 16 May 2016
Payload: Connects to URLs/IPs, Downloads files

Arrival Details

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

Installation

This Trojan drops and executes the following files:

  • %User Temp%\RETR.vbs
  • %User Temp%\e049.vbs

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

Download Routine

This Trojan saves the files it downloads using the following names:

  • %User Temp%\rss_.exe

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

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}ua.com.ua/image/flags/a/log.php?f=404