PE_BRONTOK.A


 ALIASES:

Worm:Win32/Brontok.FF (Microsoft); W32/Rontokbro.gen@MM (McAfee); W32.Rontokbro.K@mm (Symantec); Email-Worm.Win32.Brontok.ai (Kaspersky); Worm.Win32.Brontok.kk (v) (Sunbelt); I-Worm/Brontok.PF (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 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:

147,456 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

26 May 2013

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.

Installation

This file infector creates the following folders:

  • %Windows%\Shell

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

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Wilbert = "%Application Data%\Wilbert.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
smss = "%Windows%\Shell\explorer.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe %Windows%\Shell\iexplorer.exe"

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

Other System Modifications

This file infector adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\NOD32krn

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\
Services\NOD32krn

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Norman ZANDA

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Norman NJeeves

It adds the following registry entries:

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

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\NOD32krn
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\
Services\NOD32krn
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Norman ZANDA
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Norman NJeeves
Start = "4"

It 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 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

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

Dropping Routine

This file infector drops the following files:

  • %Windows%\Shell\msvbvm60.dll
  • %Application Data%\msvbvm60.dll

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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 PE_BRONTOK.A using either the Startup Disk or Recovery Console

[ Learn More ]

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\SYSTEM\ControlSet001\Services
    • NOD32krn
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services
    • NOD32krn
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services
    • Norman ZANDA
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services
    • Norman NJeeves

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\CurrentVersion\Run
    • Wilbert = "%Application Data%\Wilbert.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • smss = "%Windows%\Shell\explorer.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • ShowSuperHidden = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\NOD32krn
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\NOD32krn
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Norman ZANDA
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Norman NJeeves
    • Start = "4"

Step 5

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\Advanced
    • From: HideFileExt = "1"
      To: HideFileExt = ""1""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = "2"
      To: Hidden = ""2""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe %Windows%\Shell\iexplorer.exe"
      To: Shell = ""Explorer.exe""

Step 6

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.
  • %Windows%\Shell\msvbvm60.dll
  • %Application Data%\msvbvm60.dll

Step 7

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.
  • %Windows%\Shell

Step 8

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


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