Analysis by: Rhena Inocencio
ALIASES:

Virus.VBS.Confi (Kaspersky), VBS/Redlof-A (Sophos)

 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: File infector

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This file infector 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: Varies
File Type: VBS
Initial Samples Received Date: 30 Apr 2002

Arrival Details

This file infector arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Autostart Technique

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

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
Kernel32 = "%System%\Kernel.dll"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
Kernel32 = "%Windows%\System\Kernel32.dll"

Other System Modifications

This file infector adds the following registry entries:

HKEY_CLASSES_ROOT\dllfile\shell\
open\command
Default = "%Windows%\WScript.exe "%1" %*"

HKEY_CLASSES_ROOT\dllfile\ScriptEngine
Default = "VBScript"

HKEY_CLASSES_ROOT\dllfile\ShellEx\
PropertySheetHandlers\WSHProps
Default = "{60254CA5-953B-11CF-8C96-00AA00B8708C}"

HKEY_CLASSES_ROOT\dllfile\ScriptHostEncode
Default = "{85131631-480C-11D2-B1F9-00C04F86C324}"

File Infection

This file infector infects the following files:

  • VBS
  • HTML
  • HTM
  • ASP
  • PHP
  • JSP
  • HTT

NOTES:

It checks if the file %Windows%\wscript.exe exists. If it finds the said file, it creates a copy of itself as %System%\Kernel.dll.

If the file %Windows%\wscript.exe is not found, it drops a copy of itself as %Windows%\System\Kernel32.dll.

  SOLUTION

Minimum Scan Engine: 9.300
VSAPI OPR PATTERN File: 1.587.00
VSAPI OPR PATTERN Date: 30 Apr 2002

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

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
    • Kernel32 = "%System%\Kernel.dll"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • Kernel32 = "%Windows%\System\Kernel32.dll
  • In HKEY_CLASSES_ROOT\dllfile\shell\open\command
    • Default = "%Windows%\WScript.exe "%1" %*"
  • In HKEY_CLASSES_ROOT\dllfile\ScriptEngine
    • Default = "VBScript"
  • In HKEY_CLASSES_ROOT\dllfile\ShellEx\PropertySheetHandlers\WSHProps
    • Default = "{60254CA5-953B-11CF-8C96-00AA00B8708C}"
  • In HKEY_CLASSES_ROOT\dllfile\ScriptHostEncode
    • Default = "{85131631-480C-11D2-B1F9-00C04F86C324}"

Step 3

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.  

  • %System%\Kernel32.dll

Step 4

Scan your computer with your Trend Micro product to clean files detected as VBS_REDLOF.A. 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.

NOTES:
There is no need to manually restore FOLDER.HTT, since it can already be restored by scanning the infected system with Trend Micro antivirus.


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