VBS_AUTORUN.SMC

October 08, 2012
 Analysis by: Michael Cabel
 PLATFORM:

Windows 98, ME, NT, 2000, XP, Server 2003

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes


  TECHNICAL DETAILS

File Size:

12,296 bytes

File Type:

Script

Memory Resident:

Yes

Installation

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

  • %System%\killVBS.vbs

(Note: %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 modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = %System%\userinit.exe,%System%\wscript.exe %System%\killVBS.vbs

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

Other System Modifications

This worm adds the following registry keys:

HKEY_CLASSES_ROOT\VBSFile
DefaultIcon = %System%\WScript.exe,2

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Window Title = ""

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Start Page = ""

(Note: The default value data of the said registry entry is {User Defined}.)

Propagation

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

  • killVBS.vbs

  SOLUTION

Minimum Scan Engine:

8.900

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

Identify and delete files detected as VBS_AUTORUN.SMC using the Recovery Console

[ Learn More ]

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_CLASSES_ROOT\VBSFile
    • DefaultIcon=%System%\WScript.exe,2
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Window Title=

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Userinit=%System%\userinit.exe,%System%\wscript.exe %System%\killVBS.vbs
      To: Userinit=%System%\userinit.exe,
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • From: Start Page=
      To: Start Page={User Defined}

Step 5

Scan your computer with your Trend Micro product to delete files detected as VBS_AUTORUN.SMC. 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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