Analysis by: Jimelle Monteser
ALIASES:

Worm:Win32.VB.faw (Kaspersky), Worm:Win32/Amend.A (Microsoft), W32.Rarbeauty@mn (Norton)

 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:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Size: 196,608 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 28 Jun 2013

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:

  • %System%\msconfig.exe
  • %System%\regedit.exe
  • %System%\regedit32.exe
  • %Windows%\Fonts\taskmgr.exe
  • %Temp%\ctfmon.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.. %Windows% is the Windows folder, which is usually C:\Windows.. %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)

Autostart Technique

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

  • %ProgramData%\Microsoft\Windows\Start Menu\Programs\Startup\startup.bat - for Windows 7 (copy of itself)
  • %All Users Profile%\Start Menu\Programs\Startup\startup.bat - for Windows XP (copy of itselft)

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).. %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

Other System Modifications

This worm adds the following registry entries:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\LanmanServer\Parameters
AutoShareWks = "1"

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\LanmanServer\Parameters
AutoShareServer = "1"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Setup
intt = "%Windows%\Fonts\taskmgr.exe"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "0"

(Note: The default value data of the said registry entry is "1".)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "1"

(Note: The default value data of the said registry entry is "0".)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CabinetState
FullPath = "1"

(Note: The default value data of the said registry entry is "0".)

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "C:\WINDOWS\system32\userinit.exe,regedit32.com"

(Note: The default value data of the said registry entry is "C:\WINDOWS\system32\userinit.exe".)

Propagation

This worm searches for folders in all physical and removable drives then drops copies of itself inside the folder as {folder name}.EXE.

It drops the following copy of itself in all physical and removable drives:

  • {Drive Letter}:\Comand.com

Dropping Routine

This worm drops the following files:

  • {Drive Letter}:\folder.htt
  • {Drive Letter}:\desktop.ini
  • {Drive Letter}:\autorun.inf

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.122.02
FIRST VSAPI PATTERN DATE: 28 Jun 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

Since this malware cannot be removed in normal and safe mode, it is necessary to restart using the Windows Recovery Console. To restart the system using the Windows Recovery Console:

• On Windows XP and Server 2003 systems:

  1. Click Start>Run. In the Open input box, type secpol.msc and press Enter.
  2. In the left panel, double-click Local Policies>Security Options.
  3. In the right panel, double-click Recovery Console: Allow floppy copy and access to all drives and folders.
  4. Select Enabled and click OK.
  5. Insert the Windows Installation CD into the CD drive, then restart your computer.
  6. When prompted, press any key to boot from the CD.
  7. On the main menu, type r to go to the Recovery Console.
  8. Type the number that corresponds to the drive and directory that contains Windows (usually C:\WINDOWS) and press Enter.
  9. Type the Administrator password and press Enter.
  10. In the input box, type the following then press Enter:
    SET AllowAllPaths = TRUE
      %System%\regedit32.com
  11. Type exit and press Enter to restart the system normally.

• On Windows Vista and 7 systems:

  1. Insert your Windows Installation DVD in the DVD drive, then Press the restart button.
  2. When prompted, press any key to boot from the DVD.
  3. Depending on your Windows Installation DVD, you might be required to select the installation language. Then on the Install Windows window, choose your language, locale, and keyboard layout or input method. Click Next, then click Repair your computer.
  4. Select Use recovery tools that can help fix problems starting Windows. Select your installation of Windows. Click Next.
  5. If the Startup Repair window appears, click Cancel, Yes, then Finish.
  6. In the System Recovery Options window, click Command Prompt.
  7. In the Command Prompt window, type the following then press Enter:
      %System%\regedit32.com
    (Note: In Windows 7, all local drives will be assigned one more than normal. For example, the C: drive becomes D:.)
  8. Type exit and press Enter to close the Command Prompt window.
  9. Click Restart to restart the system normally.

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_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters
    • AutoShareWks = "1"
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters
    • AutoShareServer = "1"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Setup
    • intt = "%Windows%\Fonts\taskmgr.exe"

Step 4

Restore this modified 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\Explorer\Advanced
    • From: Hidden = "0"
      To: Hidden = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "1"
      To: HideFileExt = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
    • From: FullPath = "1"
      To: FullPath = "0"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Userinit = "%System%\userinit.exe,regedit32.com"
      To: Userinit = "%System%\userinit.exe"

Step 5

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.
  • {Drive Letter}:\folder.htt
  • {Drive Letter}:\desktop.ini
  • {Drive Letter}:\autorun.inf

Step 6

Scan your computer with your Trend Micro product to delete files detected as
WORM_VB.KJV

*Note: 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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