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VBS_AUTORUN.SML

October 08, 2012
 Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Copies itself in all available physical drives, Propagates via removable drives

This worm employs registry shell spawning by adding certain registry entries. This allows this malware to execute even when other applications are opened.

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.

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size:

724,616 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

03 Dec 2010

Payload:

Drops files

Installation

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

  • %System%\winjpg.jpg

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

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

It employs registry shell spawning to ensure its execution when certain file types are accessed by adding the following entries:

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"

Other System Modifications

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

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

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

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

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusOverride = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows Script Host\Settings
Enabled = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Installer
LimitSystemRestoreCheckpointing = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows NT\SystemRestore
DisableSR = 1

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

HKEY_CLASSES_ROOT\mp3file
FriendlyTypeName = "Good Songs"

(Note: The default value data of the said registry entry is "%Windows%\inf\unregmp2.exe,-10002".)

HKEY_CLASSES_ROOT\VBSFile
FriendlyTypeName = "MP3 Audio"

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

HKEY_CLASSES_ROOT\VBSFile\DefaultIcon
(Default) = "%Program Files%\WINDOW~3\wmplayer.exe,-120"

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoDriveTypeAutoRun = 0

(Note: The default value data of the said registry entry is 91.)

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.)

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
HideFileExt = 1

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

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

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

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 the following copy of itself in all physical and removable drives:

  • winfile.jpg

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

Dropping Routine

This worm drops the following files:

  • %System%\winxp.exe - detected as BKDR_BIFROSE.DPW

(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 executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

Other Details

This worm does the following:

  • It creates the following registry entries to enable automatic execution everytime an associated application is run:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
    Windows NT\CurrentVersion\Image File Execution Options\{Applications Executable File Name}
    Debugger = "%System%\wscript.exe /E:vbs %System%\winjpg.jpg"

    {Applications Executable File Name} has the following values:

    • MSConfig.exe
    • procexp.exe
    • regedit.exe
    • taskmgr.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.)

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.701.00

FIRST VSAPI PATTERN DATE:

15 Dec 2010

VSAPI OPR PATTERN File:

7.701.00

VSAPI OPR PATTERN Date:

15 Dec 2010

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 files dropped/downloaded by VBS_AUTORUN.SML

     BKDR_BIFROSE.DPW

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Enable Registry Editor

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

Step 5

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
    • CTFMON = %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
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Scripting Host\Settings
    • DisplayLogo = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Scripting Host\Settings
    • Timeout = 0
  • 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_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • AntiVirusOverride = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Script Host\Settings
    • Enabled = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Installer
    • LimitSystemRestoreCheckpointing = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\SystemRestore
    • DisableSR = 1

Step 6

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 NT\CurrentVersion\Image File Execution Options
    • MSConfig.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • procexp.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • regedit.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • taskmgr.exe

Step 7

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_CLASSES_ROOT\mp3file
    • From: FriendlyTypeName = Good Songs
      To: %Windows%\inf\unregmp2.exe,-10002
  • In HKEY_CLASSES_ROOT\VBSFile
    • From: FriendlyTypeName = MP3 Audio
      To: %System%\wshext.dll,-4802,
  • In HKEY_CLASSES_ROOT\VBSFile\DefaultIcon
    • From: (Default) = %Program Files%\WINDOW~3\wmplayer.exe,-120
      To: %SystemRoot%\System32\WScript.exe,2
  • 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: HideFileExt = 1
      To: 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = 0
      To: 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • From: NoDriveTypeAutoRun = 0
      To: 91
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = 0
      To: 1
  • 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

Step 8

Search and delete AUTORUN.INF files created by VBS_AUTORUN.SML that contain these strings

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

Step 9

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