WORM_BRONTOK.FA
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
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 disables Task Manager, Registry Editor, and Folder Options.
TECHNICAL DETAILS
103,047 bytes
EXE
Yes
07 May 2011
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:
- %Windows%\SHELLNEW\bronstab.exe
- %Application Data%\smss.exe
- %Application Data%\services.exe
- %Application Data%\lsass.exe
- %Application Data%\inetinfo.exe
- %Application Data%\csrss.exe
- %Application Data%\winlogon.exe
- %User Profile%\TEMPLATES\WOWTUMPEH.COM
- %Windows%\system32\{user name}'S SETTING.SCR
- %Windows%\system32\drivers\etc\HOSTS-DENIED BY-{user name}.COM
- %Windows%\explorasi.exe
(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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.. %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.)
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
Tok-Cirrhatus = "%Application Data%\smss.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Bron-Spizaetus = "%Windows%\ShellNew\bronstab.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%\explorasi.exe"
(Note: The default value data of the said registry entry is "Explorer.exe".)
It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:
- %User Startup%\Empty.pif – copy of itself
(Note: %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.)
Other System Modifications
This worm adds the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "0"
It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:
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"
Dropping Routine
This worm drops the following files:
- %Application Data%\UPDATE.8.BRON.TOK.BIN
- %Application Data%\LISTHOST8.TXT
(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.)
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
SOLUTION
8.900
9.150.02
29 May 2012
9.151.00
29 May 2012
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
Terminate a malware/grayware process
*Note: If the detected process is not displayed in theWindows Task Manager, continue doing the next steps.
- %Application Data%\smss.exe
- %Application Data%\services.exe
- %Application Data%\lsass.exe
- %Application Data%\inetinfo.exe
- %Application Data%\csrss.exe
- %Application Data%\winlogon.exe
- %Windows%\SHELLNEW\bronstab.exe
- %User Profile%\TEMPLATES\WOWTUMPEH.COM
- %Windows%\EKSPLORASI.PIF
Step 3
To enable Registry Editor, Task Manager, and Folder options:
- Open Notepad. To do this, click Start>Run, type Notepad in the text box provided, then press Enter.
- Copy and paste the following script:
- Save this file as C:RESTORE.VBS.
- Click Start>Run again, type C:RESTORE.VBS in the text box provided, then press Enter.
- Click Yes at the prompt of the message box to execute the .VBS file.
Step 4
Delete this registry value
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
- Bron-Spizaetus = "%Windows%\ShellNew\bronstab.exe"
- Bron-Spizaetus = "%Windows%\ShellNew\bronstab.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Tok-Cirrhatus = "%Application Data%\smss.exe"
- Tok-Cirrhatus = "%Application Data%\smss.exe"
Step 5
Search and delete these files
- %Application Data%\UPDATE.8.BRON.TOK.BIN
- %Application Data%\LISTHOST8.TXT
Step 6
Scan your computer with your Trend Micro product to delete files detected as WORM_BRONTOK.FA. 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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