JS_NEMUCOD.DLDVFS

October 10, 2016
 Analysis by: Janus Agcaoili
 ALIASES:

TrojanDownloader:JS/Nemucod.HG (Microsoft), Trojan-Downloader.JS.Agent.mrm (Kaspersky), JS.Downloader (Symantec)

 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:

Propagates via email

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

It does not have any propagation routine.

It does not have any backdoor routine.

It downloads a file from a certain URL then renames it before storing it in the affected system. It executes downloaded files whose malicious routines are exhibited by the affected system.

  TECHNICAL DETAILS

File Size:

94,982 bytes

File Type:

JS

Memory Resident:

No

Initial Samples Received Date:

07 Oct 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.

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Download Routine

This Trojan downloads files from the following URLs then renames them before storage in the affected system:

  • http://{BLOCKED}ne.net/60hrvv
  • http://{BLOCKED}atha.com/5nx311
  • http://{BLOCKED}sigortam.net/njahqfis
  • http://{BLOCKED}tsavvy.com/ncxgkw9c
  • http://{BLOCKED}r.com/nrnrwy

It saves the files it downloads using the following names:

  • %User Temp%\yMIy7JjkwqE8UK <- encrypted download file
  • %User Temp%\yMIy7JjkwqE8UK.dll <- decrypted download file

(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:

  • Variants of Locky ransomware family

It executes downloaded files :

  • %User Temp%\yMIy7JjkwqE8UK.dll

(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.)

whose malicious routines are exhibited by the affected system.

NOTES:

A temporary file of the encrypted download file may be created in the %Temporary Internet Files%\Content.IE5\{random subfolder name} as a by-product of the download routine.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.816.08

FIRST VSAPI PATTERN DATE:

04 Oct 2016

VSAPI OPR PATTERN File:

12.817.00

VSAPI OPR PATTERN Date:

05 Oct 2016

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 Temp%\yMIy7JjkwqE8UK
%User Temp%\yMIy7JjkwqE8UK.dll\

Step 4

Scan your computer with your Trend Micro product to delete files detected as JS_NEMUCOD.DLDVFS. 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.

NOTES:

Clear or Delete the files in the %Temporary Internet Files%\Content.IE5 folder.


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