Worm.JS.NEMUCOD.WEALSW

July 26, 2019
 Analysis by: Henry Alarcon Jr.
 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

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

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

690,734 bytes

File Type:

Other

Initial Samples Received Date:

25 Jul 2019

Payload:

Displays windows, Connects to URLs/IPs, Downloads files, Terminates processes

Arrival Details

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

It may be dropped by the following malware:

Installation

This Worm drops the following files:

  • %User Temp%\ascii.txt

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • cmd /U /Q /C cd /D : && dir /b/s/x *.doc *.xls *.pdf *.rtf *.txt *.pub *.odt *.ods *.odp *.odm *.odc *.odb >> %TEMP%\ascii.txt
  • cmd /U /Q /C copy /Y "{Malware File Directory}\{Malware File Name}" "{Name of the File it will replace}.jse && del /Q/F {Name of the File it will replace}"

Autostart Technique

This Worm drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\shell.jse

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows 2003(32-bit), XP and 2000(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit), 10(64-bit).)

Other Details

This Worm connects to the following possibly malicious URL:

  • https://{BLOCKED}.{BLOCKED}.82.15/hollyhole/c644.php

It does the following:

  • If it fails to download a file from its C&C Server, it locates for files with the following extensions in shared and removable drives, deletes the file and replaces the deleted file with a copy of itself:
    • .doc
    • .xls
    • .pdf
    • .rtf
    • .txt
    • .pub
    • .odt
    • .ods
    • .odp
    • .odm
    • .odc
    • .odb

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.258.06

FIRST VSAPI PATTERN DATE:

26 Jul 2019

VSAPI OPR PATTERN File:

15.259.00

VSAPI OPR PATTERN Date:

27 Jul 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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

Identify and terminate files detected as Worm.JS.NEMUCOD.WEALSW

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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 Startup%\shell.jse
  • %User Temp%\ascii.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as Worm.JS.NEMUCOD.WEALSW. 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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