WORM_BRONTOK.WBK


 ALIASES:

Worm:Win32/Brontok.FFV (Microsoft), HEUR:Trojan.Win32.Generic (Kaspersky), W32.SillyFDC (Symantec), I-Worm/Brontok.AC (AVG), W32/Brontok-CJ (Sophos), W32/IRCBot.PBR!tr (Fortinet), Win32/VB.NJG worm (Nod32), W32/Brontok.EX.worm (Panda), Backdoor.Win32.IRCBot.pbr (v) (Sunbelt)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Via physical/removable drives, Propagates via removable drives

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 creates certain registry entries to prevent execution of files with certain file types.

It drops copies of itself in all removable drives.

  TECHNICAL DETAILS

File Size:

40,960 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

26 Jun 2014

Payload:

Drops files

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 Drive%\(Read Me)Pendekar Blank.txt

It drops the following component file(s):

  • %System Drive%\msvbvm60.dll
  • %System%\dllchache\msvbvm60.dll
  • %System%\dllcache\msvbvm60.dll

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

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

  • %System Drive%\AUT0EXEC.BAT
  • %System%\M5VBVM60.EXE
  • %System%\rund1132.exe
  • %System%\dllchache.exe
  • %System%\dllcache\Regedit32.com
  • %System%\dllcache\Shell32.com
  • %System%\dllchache\Unoccupied.reg
  • %System%\dllchache\Zero.txt
  • %System%\dllchache\Blank.doc
  • %System%\dllchache\Empty.jpg
  • %System%\dllchache\Hole.zip
  • %Windows%\system32.exe

It creates the following folders:

  • %System%\dllchache

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Secure64 = "%System%\dllcache\Regedit32.com StartUp"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Secure32 = "%System%\dllcache\Shell32.com StartUp"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Blank AntiViri = "%System Root%\AUT0EXEC.BAT StartUp"

It 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%\M5VBVM60.EXE StartUp""

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

It modifies the following entry(ies) to allow itself to run on safe mode:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot
AlternateShell = "%System Root%\AUT0EXEC.BAT StartUp"

(Note: The default value data of the said registry entry is "cmd.exe".)

Other System Modifications

This worm modifies the following registry entries:

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_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CabinetState
FullPath = 1

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

It creates the following registry entries to prevent execution of files with certain file types:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
comfile\shell\open\
command
(default) = "%System%\rund1132.exe %1"

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

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
txtfile\shell\open\
command
(default) = "%System%\rund1132.exe %1"

(Note: The default value data of the said registry entry is "%System%\NOTEPAD.EXE %1".)

Propagation

This worm drops copies of itself in all removable drives.

Dropping Routine

This worm sets the attributes of its dropped file(s) to the following:

  • Read Only
  • Hidden
  • System

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.868.02

FIRST VSAPI PATTERN DATE:

17 Jun 2014

VSAPI OPR PATTERN File:

10.869.00

VSAPI OPR PATTERN Date:

17 Jun 2014

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

Identify and delete files detected as WORM_BRONTOK.WBK using either the Startup Disk or 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Secure64 = "%System%\dllcache\Regedit32.com StartUp"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Secure32 = "%System%\dllcache\Shell32.com StartUp"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Blank AntiViri = "%System Root%\AUT0EXEC.BAT StartUp"

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\SYSTEM\CurrentControlSet\Control\SafeBoot
    • From: AlternateShell = "%System Root%\AUT0EXEC.BAT StartUp"
      To: AlternateShell = "cmd.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Userinit = "%System%\userinit.exe, "%System%%\M5VBVM60.EXE StartUp""
      To: Userinit = "%System%\userinit.exe,"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "1"
      To: HideFileExt = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "0"
      To: ShowSuperHidden = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
    • From: FullPath = "1"
      To: FullPath = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\comfile\shell\open\command
    • From: (default) = "%System%\rund1132.exe %1"
      To: (default) = ""%1" %*"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\txtfile\shell\open\command
    • From: (default) = "%System%\rund1132.exe %1"
      To: (default) = "%System%\NOTEPAD.EXE %1"

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %System%\dllchache

Step 6

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %System Drive%\AUT0EXEC.BAT
  • %System%\M5VBVM60.EXE
  • %System%\rund1132.exe
  • %System%\dllchache.exe
  • %System%\dllcache\Regedit32.com
  • %Windows%\system32.exe
  • %System Drive%\msvbvm60.dll
  • %System%\dllchache\msvbvm60.dll
  • %System%\dllcache\msvbvm60.dll
  • %System Drive%\(Read Me)Pendekar Blank.txt

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_BRONTOK.WBK. 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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