ALIASES:

Worm:Win32/Brontok.FFV (Microsoft); W32/Rontokbro.worm (McAfee); W32.SillyFDC (Symantec); HEUR:Trojan.Win32.Generic (Kaspersky); Mal/Behav-344 (Sophos); Backdoor.Win32.IRCBot.pbr (v) (Sunbelt); Trojan horse Generic32.RRU (AVG)

 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: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm 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: 67,072 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 05 Jun 2014

Arrival Details

This worm 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 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_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Blank AntiViri = "%System Root%\AUT0EXEC.BAT 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"

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 %Windows%\system32\userinit.exe,.)

Other System Modifications

This worm adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CabinetState
FullPathAddress = "1"

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

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CabinetState
FullPath = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "1"

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "1"

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

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\SafeBoot
AlternateShell = "%System Root%\AUT0EXEC.BAT StartUp"

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

Dropping Routine

This worm drops the following files:

  • %System Root%\(Read Me)Pendekar Blank.txt
  • %System%\dllChache\msvbvm60.dll
  • %System Root%\msvbvm60.dll
  • %System%\dllcache\msvbvm60.dll
  • %System%\dllChache\Empty.jpg
  • %System%\dllChache\Blank.doc
  • %System%\dllChache\Zero.txt
  • %System%\dllChache\Hole.zip
  • %System%\dllChache\Unoccupied.reg
  • %System Root%\AUT0EXEC.BAT
  • %System%\rund1132.exe
  • %System%\dllcache\Regedit32.com
  • %System%\dllcache\Shell32.com
  • %System%\M5VBVM60.EXE
  • %System%.exe
  • %System%\dllchache.exe

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.700

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.WB 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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Blank AntiViri = "%System Root%\AUT0EXEC.BAT StartUp"
  • 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
    • FullPathAddress = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • ShowSuperHidden = "0"

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
    • FullPath = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = "1"
      To: Hidden = ""2""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "1"
      To: HideFileExt = ""1""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\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 = ""%Windows%\system32\userinit.exe,""

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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 Root%\(Read Me)Pendekar Blank.txt
  • %System%\dllChache\msvbvm60.dll
  • %System Root%\msvbvm60.dll
  • %System%\dllcache\msvbvm60.dll
  • %System%\dllChache\Empty.jpg
  • %System%\dllChache\Blank.doc
  • %System%\dllChache\Zero.txt
  • %System%\dllChache\Hole.zip
  • %System%\dllChache\Unoccupied.reg
  • %System Root%\AUT0EXEC.BAT
  • %System%\rund1132.exe
  • %System%\dllcache\Regedit32.com
  • %System%\dllcache\Shell32.com
  • %System%\M5VBVM60.EXE
  • %System%.exe
  • %System%\dllchache.exe

Step 6

Search and delete this folder

[ 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 7

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