Analysis by: MarfelTi
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • 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.

It modifies registry entries to hide files with System and Read-only attributes.

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

  TECHNICAL DETAILS

File Size: 344,708 bytes
File Type: VBS
Initial Samples Received Date: 16 May 2011
Payload: Disables Registry Editor

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 files:

  • %System%\win.exe

(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.)

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

  • %system%\winjpg.jpg

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
regdiit = %system%\winxp.exe

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
CTFMON = "%System%\wscript.exe /E:vbs %System%\winjpg.jpg

Other System Modifications

This worm adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows Script Host\Settings
DisplayLogo = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows Script Host\Settings
Timeout = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows Scripting Host\Settings
DisplayLogo = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows Scripting Host\Settings
Timeout = 0

It adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
MSConfig.exe
Debugger = %System%\wscript.exe /E:vbs %System%\winjpg.jpg

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
drwtsn32.exe
Debugger = %System%\wscript.exe /E:vbs %System%\winjpg.jpg

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
dwwinxp.exe
Debugger = %System%\wscript.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
rstrui.exe
Debugger = %System%\wscript.exe /E:vbs %System%\winjpg.jpg

HKEY_CLASSES_ROOT\exefile\shell\
Open application\command
(Default) = %system%\winxp.exe

HKEY_CLASSES_ROOT\exefile\shell\
Scan for virus,s\command
(Default) = %System%\wscript.exe /E:vbs %System%\winjpg.jpg

It modifies the following registry entries:

HKEY_CURRENT_USER\SOFTWARE\MICROSOFT\
Windows\CURRENTVERSION\ Policies\
Explorer
NoDriveTypeAutoRun = 0

(Note: The default value data of the said registry entry is 95.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = 4

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = 4

(Note: The default value data of the said registry entry is 2.)

HKEY_CLASSES_ROOT\VBSFile
FriendlyTypeName = MP3 Audio

(Note: The default value data of the said registry entry is @%System%\wshext.dll,-4802.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusOverride = 1

(Note: The default value data of the said registry entry is 0.)

It modifies the following registry entries to hide files with System and Read-only attributes:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CURRENTVERSION\Explorer\
Advanced
Hidden = 0

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

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CURRENTVERSION\Explorer\
Advanced
SuperHidden = 0

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

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CURRENTVERSION\Explorer\
Advanced
ShowSuperHidden = 0

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

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CURRENTVERSION\Explorer\
Advanced
HideFileExt = 1

(Note: The default value data of the said registry entry is 0.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = 0

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

Propagation

This worm 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]
shellexecute=Wscript.exe /e:vbs winfile.jpg

  SOLUTION

Minimum Scan Engine: 8.900

Step 1

Restart in Safe Mode

[ Learn More ]

Step 2

Enable Registry Editor

[ Learn More ]
By doing this step, you also enable other applications/programs disabled by this malware/grayware/spyware.

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\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • regdiit = %system%\winxp.exe
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • CTFMON = %System%\wscript.exe /E:vbs %System%\winjpg.jpg
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\MSConfig.exe
    • Debugger = %System%\wscript.exe /E:vbs %System%\winjpg.jpg
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\drwtsn32.exe
    • Debugger = %System%\wscript.exe /E:vbs %System%\winjpg.jpg
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\dwwinxp.exe
    • Debugger = %System%\wscript.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\rstrui.exe
    • Debugger = %System%\wscript.exe /E:vbs %System%\winjpg.jpg
  • In HKEY_CLASSES_ROOT\exefile\shell\Open application\command
    • (Default) = %system%\winxp.exe
  • In HKEY_CLASSES_ROOT\exefile\shell\Scan for virus,s\command
    • (Default) = %System%\wscript.exe /E:vbs %System%\winjpg.jpg

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_CURRENT_USER\Software\Microsoft\Windows Script Host\Settings
    • DisplayLogo = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Script Host\Settings
    • Timeout = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Scripting Host\Settings
    • DisplayLogo = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Scripting Host\Settings
    • Timeout = 0

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\ Policies\Explorer
    • From: NoDriveTypeAutoRun = 0
      To: 95
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
    • From: Start = 4
      To: 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
    • From: Start = 4
      To: 2
  • In HKEY_CLASSES_ROOT\VBSFile
    • From: FriendlyTypeName = MP3 Audio
      To: @%System%\wshext.dll,-4802
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: AntiVirusOverride = 1
      To: 0
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CURRENTVERSION\Explorer\Advanced
    • From: Hidden = 0
      To: 1
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CURRENTVERSION\Explorer\Advanced
    • From: SuperHidden = 0
      To: 1
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CURRENTVERSION\Explorer\Advanced
    • From: ShowSuperHidden = 0
      To: 1
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CURRENTVERSION\Explorer\Advanced
    • From: HideFileExt = 1
      To: 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = 0
      To: 1

Step 6

Search and delete AUTORUN.INF files created by VBS_SOLOW.BT that contain these strings

[ Learn More ]


[autorun]
shellexecute=Wscript.exe /e:vbs winfile.jpg

Step 7

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