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WORM_VB.CVL

October 09, 2012
 Analysis by: Anthony Joe Melgarejo
 ALIASES:

Worm:Win32/SillyFDC (Microsoft), W32/USBCasv (McAfee), W32.SillyFDC (Symantec), Win32/VB.FP worm (NOD32), Trojan.Win32.Generic!BT (Sunbelt)

 PLATFORM:

Windows 2000, XP, Server 2003

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This worm arrives by connecting affected removable drives to a system. 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:

93,612 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Apr 2004

Arrival Details

This worm arrives by connecting affected removable drives to a system.

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 files:

  • %Windows%\uda.exe
  • %System%\mswinsck.ocx
  • %System%\Recycled\desktop.ini

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It drops the following copies of itself into the affected system:

  • %User Temp%\s.exe
  • %System%\odbcasvc.exe
  • %System%\Recycled\INFO.EXE

(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.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

This worm registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\odbcasvc

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_ODBCASVC

Other System Modifications

This worm adds the following registry entries:

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Policies\Exploer
NoDriveTypeAutoRun = "ff"

Propagation

This worm modifies the contents of an existing AUTORUN.INF file to automatically execute its dropped copy. It does this by adding the following strings in the .INF file:

  • [autorun]
  • open=.\recycled\info.exe
  • shell\1=S»++
  • shell\1\Command=.\recycled\info.exe
  • shellexecute=.\recycled\info.exe

NOTES:

It also drops the following AUTORUN.INF on the Windows system folder:

  • %System%\autorun.inf

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

4.384.03

FIRST VSAPI PATTERN DATE:

02 Apr 2007

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

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\SYSTEM\CurrentControlSet\Services
    • odbcasvc
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_ODBCASVC

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_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Policies\Exploer
    • NoDriveTypeAutoRun = "ff"

Step 5

Search and delete AUTORUN.INF files created by WORM_VB.CVL that contain these strings

[ Learn More ]
[autorun]
open=.\recycled\info.exe
shell\1=S»++
shell\1\Command=.\recycled\info.exe
shellexecute=.\recycled\info.exe

Step 6

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