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VBS_DUNIHI.TUOD

April 20, 2015
 Analysis by: Christopher Daniel So
 ALIASES:

VBS/Agent.OOV (Panda)

 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:

Propagates via removable drives, Downloaded from the Internet, Dropped by other malware


This worm arrives via removable drives. It 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.

It gathers certain information on the affected computer.

  TECHNICAL DETAILS

File Size:

221,363 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

11 Apr 2015

Payload:

Compromises system security

Arrival Details

This worm arrives via removable drives.

It 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:

  • %User Temp%\{malware file name and extension}
  • %User Startup%\{malware file name and extension}

(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.. %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, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

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 file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
{malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"

Propagation

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

  • {removable drive letter}:\{malware file name and extension}

Backdoor Routine

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

  • update - Update malware code in %User Temp%\{malware file name and extension} and restart the malware
  • uninstall - Uninstall the malware
  • send - Download and run a file from the C&C server
  • site-send - Download and run a file
  • recv - Send a file to the C&C server
  • enum-driver - Send list of drives
  • enum-faf - Enumerate folders and files contained in a folder
  • enum-process - List running processes
  • cmd-shell - Execute a command using Command Prompt
  • delete - Delete a file or folder
  • exit-process - Terminate a process

(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.)

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

  • http://{BLOCKED}9.linkpc.net:2026/

Information Theft

This worm gathers the following information on the affected computer:

  • Volume serial number
  • Computer name
  • Current user name
  • OS name
  • Installed AV products

NOTES:
It drops .LNK files whose names correspond to the files and folders in the root directory of the removable drive. When the .LNK files are double clicked, the dropped copy in the removable drive's root directory is executed.

  SOLUTION

Minimum Scan Engine:

9.750

VSAPI OPR PATTERN File:

11.597.00

VSAPI OPR PATTERN Date:

11 Apr 2015

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

Restart in Safe Mode

[ Learn More ]

Step 3

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 file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • {malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"

Step 4

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 Startup%\{malware file name and extension}

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as VBS_DUNIHI.TUOD. 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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