Analysis by: Nikko Tamana
ALIASES:

Worm:VBS/Dunihi.O (Microsoft)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  TECHNICAL DETAILS

File Size: 50,769 bytes
File Type: VBS
Memory Resident: Yes
Initial Samples Received Date: 13 Sep 2013
Payload: Downloads files, 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}.vbs

(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 and 7.)

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}.vbs""

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{Malware File Name} = "wscript.exe //B "%User Temp%\{Malware File Name}.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 File Name}.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, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Other System Modifications

This worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\{Malware File Name}

It adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\{Malware File Name}
{Default} = "{true/false} - {Date of Installation}"

Propagation

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

  • {Removable Drive}:\{Malware File Name}.vbs

Backdoor Routine

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

  • Update itself
  • Uninstall itself
  • Download/Upload files
  • List Drivers
  • Perform File Management (Create, Modify, Delete)
  • List Running Processes
  • Shell Execution
  • Sleep

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

  • http://mda.{BLOCKED}p.org:88/is-ready

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

Information Theft

This worm gathers the following data:

  • Drive Information
  • Username
  • Computer Name
  • OS Information

NOTES:
This malware hides all files and folders in the root of all removable drives. For every hidden file/folder, it creates a .LNK file using its file/folder name.

If a shortcut (.LNK) file is executed, it then executes the dropped copy of VBS_HOUSCORP.A in the removable drive.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.300
VSAPI OPR PATTERN File: 10.295.00
VSAPI OPR PATTERN Date: 23 Sep 2013

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

Scan your computer with your Trend Micro product and note files detected as VBS_HOUSCORP.A

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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 File Name}

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {Malware File Name} = "wscript.exe //B "%User Temp%\{Malware File Name}.vbs""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {Malware File Name} = "wscript.exe //B "%User Temp%\{Malware File Name}.vbs""

Step 6

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%\{Malware File Name}.vbs
  • %User Startup%\{Malware File Name}.vbs
  • {Removable Drive}:\{Malware File Name}.vbs

Step 7

  1. Open a command prompt.
    • For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run. In the Search box, type CMD then press Enter.
    • For Windows Vista and Windows 7 users, click Start, type CMD in the Search input field then press Enter.
  2. In the CMD console, type the following:

    ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [+I | -I] [drive:][path][file name] [/S [/D] [/L]]

    Where:
    + Sets an attribute.
    - Clears an attribute
    R Read-only file attribute
    A Archive file attribute
    S System file attribute
    H Hidden file attribute
    I Not content indexed file attribute
    [drive:][path][filename]
    Specifies a file or files for attrib to process
    /S Processes matching files in the current folder and all subfolders.
    /D Processes folders
    /L Work on the attributes of the Symbolic Link versus the target of the Symbolic Link
    Example:
    To unhide all files and folders (including subfolders) in drive D:
    ATTRIB –H D:\* /S /D
  3. Repeat Step 3 for folders and files in other drives or directories.

Step 8

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

NOTES:
Delete all the shortcut (.LNK) files created by VBS_HOUSCORP.A in each removable drive present. Unhide all the files/folders in the root of the removable drives.


Did this description help? Tell us how we did.