WORM_IMVB.B

 Analysis by: Jimelle Monteser

 ALIASES:

IM-Worm.Win32.VB.py (Kaspersky), W32/VBTrojan.17E!Maximus (FPROT), IM-Worm.Win32.VB (Ikarus), a variant of Win32/VB.NZK worm (NOD32),

 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:

  • 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:

61,440 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Mar 2014

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:

  • %Windows%\system\Fun.exe
  • %System%\dc.exe
  • %System%\sviq.exe
  • %System%\WinSit.exe
  • %System%\config\Win.exe
  • {Removable Drive Letter}:\{folder name}\{folder name}.exe

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

Autostart Technique

This worm modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe %System%\WinSit.exe"

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Init = "%System%\config\Win.exe"

(Note: The default value data of the said registry entry is "%System%\userinit.exe,".)

Dropping Routine

This worm drops the following files:

  • %Windows%\repair.ini

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

NOTES:

This worm searches for folders in all removable drives then drop copies of itself inside the folder as {folder name}.exe.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.676.02

FIRST VSAPI PATTERN DATE:

20 Mar 2014

VSAPI OPR PATTERN File:

10.677.00

VSAPI OPR PATTERN Date:

21 Mar 2014

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

Identify and delete files detected as WORM_IMVB.B using either the Startup Disk or Recovery Console

[ Learn More ]

Step 3

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe %System%\WinSit.exe"
      To: Shell = "Explorer.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Init = "%System%\config\Win.exe"
      To: Init = "%System%\userinit.exe,"

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.
  • %Windows%\repair.ini

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_IMVB.B. 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.


Did this description help? Tell us how we did.