JS_DLOADR.YYSTT

July 07, 2017
 Analysis by: John Anthony Banes
 ALIASES:

JS.Downloader (Norton); TrojanDownloader:JS/Nemucod (Microsoft); JS/DwnLdr-TTB (Sophos Lite)

 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:

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

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.

  TECHNICAL DETAILS

File Size:

55,744 bytes

File Type:

JS

Memory Resident:

No

Initial Samples Received Date:

30 Jun 2017

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.

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

This malware arrives via the following means:

  • As an embedded file on a document detected as TROJ_DLOADR.YYTBT.

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}omeskillz.co.uk/sc/
  • http://{BLOCKED}enic.co.th/plugins/user/cpcferhen/
  • http://{BLOCKED}rnetcheapskate.com/ezeofbhwy/
  • http://{BLOCKED}lland.net/eykijlaihw/
  • http://{BLOCKED}rillium.com/qtvrtgjem/

It saves the files it downloads using the following names:

  • %User Temp%\ib{6 decimal characters}.uw

(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.)

Trend Micro detects the dowloaded file as:

  • TSPY_EMOTET.XXUE, as of this writing.

NOTES:
This malware arrives through a DOCX file. It is embedded and will execute its routine upon activation by the user:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.504.04

FIRST VSAPI PATTERN DATE:

30 Jun 2017

VSAPI OPR PATTERN File:

13.505.00

VSAPI OPR PATTERN Date:

01 Jul 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 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%\ib{6 decimal characters}.uw

Step 4

Scan your computer with your Trend Micro product to delete files detected as JS_DLOADR.YYSTT. 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.


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