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Worm.VBS.DUNIHI.TVV

February 01, 2019
 Analysis by: John Donnie Celestre
 ALIASES:

VirTool:VBS/Obfuscator.TO (Microsoft), VBS.Dunihi (Symantec)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware


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.

  TECHNICAL DETAILS

File Size:

411,486 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

31 Jan 2019

Payload:

Drops files, Connects to URLs/IPs

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 and executes them:

  • %Use Profile%\{malware filename}.vbs

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
{malware filename} = wscript.exe //B "%User Profile%\{malware filename}.vbs"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{malware filename} = wscript.exe //B "%User Profile%\{malware filename}.vbs"

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

  • %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 XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\{malware filename}
{Default} = {True/False} - {Date Executed}

Propagation

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

  • {removable drives}\{malware filename}.vbs

It creates shortcut files (.LNK) disguised as folders or files located on the affected drives pointing to the malware copy.

Other Details

This Worm connects to the following possibly malicious URL:

  • 94.{BLOCKED}.{BLOCKED}.31:1603

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.784.08

FIRST VSAPI PATTERN DATE:

31 Jan 2019

VSAPI OPR PATTERN File:

14.785.00

VSAPI OPR PATTERN Date:

01 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

Restart in Safe Mode

[ Learn More ]

Step 4

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {malware filename} = wscript.exe //B "%User Profile%\{malware filename}.vbs"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {malware filename} = wscript.exe //B "%User Profile%\{malware filename}.vbs"

Step 5

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\{malware filename}
    • {Default} = {True/False} - {Date Executed}

Step 6

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%\{malware filename}.vbs
  • %User Profile%\{malware filename}.vbs
  • {removable drives}\{malware filename}.vbs
  • {removable drives}\{folder/file name}.lnk

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Worm.VBS.DUNIHI.TVV. 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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