Trojan.JS.NEMUCOD.THBBFAI

February 26, 2019
 Analysis by: John Rey Canon
 ALIASES:

Txt.Downloader.Nemucod-6865605-0 (ClamAV); 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:

Dropped by other malware, Downloaded from the Internet

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.

It executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size:

6,837 bytes

File Type:

JS

Memory Resident:

No

Initial Samples Received Date:

26 Feb 2019

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 drops and executes the following files:

  • %User Temp%\{Random File Name}.tmp

(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, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

It executes then deletes itself afterward.

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}ucviet.vn/administrator/backups/browser.jpg
  • http://{BLOCKED}vestco.ir/wp-content/themes/consulto-thecreo/languages/browser.jpg

It saves the files it downloads using the following names:

  • %Temporary Internet Files%\Content.IE5\{Random Folder Name}\browser[1].jpg

(Note: %Temporary Internet Files% is the Temporary Internet Files folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temporary Internet Files on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Microsoft\Windows\Temporary Internet Files on Windows Vista and 7, or C:\Users\{user name}\AppData\Local\Microsoft\Windows\INetCache on Windows 8.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.838.03

FIRST VSAPI PATTERN DATE:

26 Feb 2019

VSAPI OPR PATTERN File:

14.839.00

VSAPI OPR PATTERN Date:

27 Feb 2019

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%\{Random File Name}.tmp
  • %Temporary Internet Files%\Content.IE5\{Random Folder Name}\browser[1].jpg

Step 4

Scan your computer with your Trend Micro product to delete files detected as Trojan.JS.NEMUCOD.THBBFAI. 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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