Worm.VBS.DUNIHI.YYSXR

 Analysis by: Carl Jayson Peliña

 ALIASES:

Trojan-Dropper.VBS.Houdini (IKARUS); JS/Agent.BNCL!tr (FORTINET)

 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, Propagates via removable drives

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 executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

83,755 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

07 Jan 2020

Payload:

Compromises system security, Connects to URLs/IPs, Steals information

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.

Installation

This Worm drops the following copies of itself into the affected system:

  • %AppData%\{Malware Filename}.vbs
  • %User Startup%\{Malware Filename}.vbs

(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).)

It drops the following files:

  • %AppData%\KLosrawTQc.vbs -> {Trojan.VBS.OBFUS.SMB}
  • %User Startup%\KLosrawTQc.vbs -> {Trojan.VBS.OBFUS.SMB}
  • {Removable Drive}:\KLosrawTQc.lnk -> points to {Removable Drive}:\KLosrawTQc.vbs
  • {Removable Drive}:\{Malware Filename}.lnk -> points to {Removable Drive}:\{Malware Filename}.vbs
  • {Removable Drive}:\KLosrawTQc.vbs -> {Trojan.VBS.OBFUS.SMB}

(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).)

It adds the following processes:

  • wscript //B "%AppData%\KLosrawTQc.vbs"
  • %System%\schtasks.exe /create /sc minute /mo 1 /tn Skype /tr "%AppData%\{Malware Filename}.vbs
  • %System%\WScript.exe "%AppData%\{Malware Filename}.vbs"

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Autostart Technique

This Worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
CRZTWVS7ME = "%AppData%\{Malware Filename}.vbs"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
KLosrawTQc = wscript.exe //B "%AppData"\KLosrawTQc.vbs"

HLEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
KLosrawTQc = wscript.exe //B "%AppData"\KLosrawTQc.vbs"

Other System Modifications

This Worm adds the following registry entries:

HKEY_USERS\S-1-5-21-2019512041-4230814187-3178073052-1000
vw0rm = {True or False}

Propagation

This Worm drops the following copy(ies) of itself in all removable drives:

  • {Removable Drive}:\{Malware Filename}.vbs

Backdoor Routine

This Worm executes the following commands from a remote malicious user:

  • exc - Execute a command received from the C2.
  • Sc - Execute a predetermined file from %temp%.
  • RF - Execute a predetermined file from %temp% with the minimized window.
  • Up - Replace a string "|U|" from the malware to "|V|".
  • Cl - Terminate the script.
  • Un - Replace some parameter from a given command then executed it afterwards.
  • Ren - Replace a string "Pc" from the malware to a predetermined string.

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://anahowaana.{BLOCKED}kpc.com:2032/Vre
  • http://{BLOCKED}tl.com:4132/isready

Information Theft

This Worm gathers the following data:

  • Disk Volume Serial Number
  • Computer Name
  • User Name
  • Caption
  • AV Products

Other Details

This Worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\KLosrawTQc

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

15.606.08

FIRST VSAPI PATTERN DATE:

07 Jan 2020

VSAPI OPR PATTERN File:

15.607.00

VSAPI OPR PATTERN Date:

08 Jan 2020

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     
    • Downloader.VBS.TRX.XXVBS82EFF002P0005

Step 2

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 3

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 4

Identify and terminate files detected as Worm.VBS.DUNIHI.YYSXR

[ 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 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_USERS\S-1-5-21-2019512041-4230814187-3178073052-1000
    • vw0rm = {True or False}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • CRZTWVS7ME = "%AppData%\{Malware Filename}.vbs"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • KLosrawTQc = wscript.exe //B "%AppData"\KLosrawTQc.vbs"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • KLosrawTQc = wscript.exe //B "%AppData"\KLosrawTQc.vbs"

Step 6

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\KLosrawTQc

Step 7

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.  
  • %AppData%\KLosrawTQc.vbs
  • %User Startup%\KLosrawTQc.vbs
  • {Removable Drive}:\KLosrawTQc.vbs
  • {Removable Drive}:\KLosrawTQc.lnk
  • {Removable Drive}:\{Malware Filename}.lnk
  • %AppData%\{Malware Filename}.vbs
  • %User Startup%\{Malware Filename}.vbs
  • {Removable Drive}:\{Malware Filename}.vbs

Step 8

Scan your computer with your Trend Micro product to delete files detected as Worm.VBS.DUNIHI.YYSXR. 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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