PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Copies itself in all available physical drives, Propagates via removable drives

This worm arrives via removable drives.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It does not have any downloading capability.

It does not have any information-stealing capability.

  TECHNICAL DETAILS

File Size: Varies
File Type: VBS
Memory Resident: Yes
Initial Samples Received Date: 01 Feb 2012

Arrival Details

This worm arrives via removable drives.

Installation

This worm drops the following copies of itself into the affected system:

  • %Windows%\Thumbs.vbs
  • %System%\Thumbs.vbs

(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.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
AVCTRL32 = "wscript.exe %System%\Thumbs.vbs"

Other System Modifications

This worm adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer
NoFolderOptions = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoRun = "1"

It modifies the following registry entries:

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

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

HKEY_CLASSES_ROOT\vbsfile\DefaultIcon
(default) = "%SystemRoot%\System32\shell32.dll,-154"

(Note: The default value data of the said registry entry is %SystemRoot%\System32\WScript.exe,2.)

HKEY_CLASSES_ROOT\VBSFile
(default) = "Data Base File"

(Note: The default value data of the said registry entry is VBScript Script File.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows Scripting Host\Script Extensions\.VBS
(default) = "Data Base File"

(Note: The default value data of the said registry entry is VBScript Script File.)

Propagation

This worm drops the following copies of itself in all physical and removable drives:

  • Thumbs.vbs

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[AUTORUN]
&Open=wscript.exe Thumbs.vbs
shell\open=Open
shell\open\Command=wscript.exe Thumbs.vbs
shell\Explore=&Explorer
shell\Explore\Command=Explorer.exe
shell\VBS.ALLYA.B\Command=wscript.exe Thumbs.vbs
shell\VBS.ALLYA.B\Default=1
[ABOUT]
VBSName=VBS.ALLYA
VBSVersion=ENCRYPTED.B-2009
VBSAUTHOR=Iwing/Indovirus
VBSNOTE=Viva Indovirus - Coba Decoded dan Pelajari ya.. :p

Download Routine

This worm does not have any downloading capability.

Information Theft

This worm does not have any information-stealing capability.

NOTES:

The said .INF file is detected by Trend Micro as TROJ_AUTOINF.A.

This worm does not have rootkit capabilities.

This worm does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.200
VSAPI OPR PATTERN File: 8.751.00
VSAPI OPR PATTERN Date: 03 Feb 2012

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

Remove malware/grayware files dropped/downloaded by VBS_AUTORUN.SMW

    • TROJ_AUTOINF.A

Step 3

Restart in Safe Mode

[ Learn More ]

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • AVCTRL32 = "wscript.exe %System%\Thumbs.vbs"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • NoFolderOptions = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableRegistryTools = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\Cur0rentVersion\Policies\Explorer
    • NoRun = "1"

Step 5

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: ShowSuperHidden = "0"
      To: ShowSuperHidden = "1"
  • In HKEY_CLASSES_ROOT\vbsfile\DefaultIcon
    • From: (default) = "%SystemRoot%\System32\shell32.dll,-154"
      To: (default) = "%SystemRoot%\System32\WScript.exe,2"
  • In HKEY_CLASSES_ROOT\VBSFile
    • From: (default) = "Data Base File"
      To: (default) = "VBScript Script File"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Scripting Host\Script Extensions\.VBS
    • From: (default) = "Data Base File"
      To: (default) = "VBScript Script File"

Step 6

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