WORM_BRONTOK.BSX

This worm arrives by connecting affected removable drives to a system. 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 uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It modifies files, disabling programs and applications from properly running.

It drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

Arrival Details

This worm arrives by connecting affected removable drives to a system.

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 copies of itself into the affected system:

• %Application Data%\smss.exe
• %Application Data%\services.exe
• %Application Data%\lsass.exe
• %Application Data%\inetinfo.exe
• %Application Data%\csrss.exe
• %Application Data%\winlogon.exe
• %System%\{USER NAME}'S SETTING.SCR
• %System%\drivers\etc\HOSTS-DENIED BY-{USER NAME}.COM
• %User Profile%\TEMPLATES\WOWTUMPEH.COM
• %Windows%\SHELLNEW\bronstab.exe
• %Windows%\EKSPLORASI.PIF
• %User Startup%\Empty.pif

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.. %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.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

It drops the following files:

• %Application Data%\LISTHOST8.TXT
• %Application Data%\UPDATE.8.BRON.TOK.BIN

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

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
Bron-Spizaetus = "%Windows%\ShellNew\bronstab.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Tok-Cirrhatus = "%Application Data%\smss.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe "C:\WINDOWS\eksplorasi.pif""

Other System Modifications

This worm modifies the following files:

• %System Root%\AUTOEXEC.BAT

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Toolbar\ShellBrowser
{01E04581-4EEE-11D0-BFE9-00AA005B4383} = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Toolbar\Explorer
ITBarLayout = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableCMD = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFolderOptions = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\ShellNoRoam\Bags\
61\Shell
FolderType = "MyDocuments"

It modifies the following registry entries to hide files with Hidden 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".)

Propagation

This worm drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

Other Details

This worm connects to the following possibly malicious URL:

• http://www.{BLOCKED}ies.com/stabro7ok/BrontokInf8.txt
• http://www.{BLOCKED}ies.com/stabro7ok/Host8.txt