WORM_RONTKBR.GEN
W32.Rontokbro@mm (Symantec), Worm:Win32/Brontok@mm (Microsoft), Email-Worm.Win32.Brontok.q (Kaspersky)
Windows
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
Spammed via email, Dropped by other malware, Downloaded from the Internet
This Worm arrives as attachment to mass-mailed email messages. 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 the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.
However, as of this writing, the said sites are inaccessible.
TECHNICAL DETAILS
51,910 bytes
EXE
No
Connects to URLs/IPs, Restarts system
Arrival Details
This Worm arrives as attachment to mass-mailed email messages.
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\sempalong.exe
- %Windows%\BerasJatah.exe
- %AppDataLocal%\csrss.exe
- %System Root%\autoexec.bat
- %User Startup%\Empty.pif
- %ApplicationData%\Microsoft\Windows\Templates\Brengkolang.com
It drops the following copies of itself into the affected system and executes them:
- %AppDataLocal%\smss.exe
- %AppDataLocal%\services.exe
- %AppDataLocal%\lsass.exe
- %AppDataLocal%\inetinfo.exe
- %AppDataLocal%\winlogon.exe
(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.)
It creates the following folders:
- %AppDataLocal%\Bron.tok-{mm}-{dd}
(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.)
It uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.
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 = "%AppDataLocal%\smss.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Bron-Spizaetus = "%Windows%\ShellNew\sempalong.exe"
It modifies the following entry(ies) to allow itself to run on safe mode:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = Explorer.exe "%Windows%\BerasJatah.exe"
(Note: The default value data of the said registry entry is Explorer.exe.)
Other System Modifications
This Worm modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableCMD = 0
(Note: The default value data of the said registry entry is 1.)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFolderOptions = 1
(Note: The default value data of the said registry entry is 0.)
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.)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = 1
(Note: The default value data of the said registry entry is 0.)
Dropping Routine
This Worm drops the following files:
- %AppDataLocal%\Update.14.Bron.Tok.bin
(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.)
Other Details
This Worm connects to the following possibly malicious URL:
- http://www.{BLOCKED}ies.com/sbllma5/IN14WHOXOLPD.txt
- http://www.{BLOCKED}ies.com/sblppt4/IN14SDSDWWHOX.txt
It sets the attributes of the following file(s) to Hidden and System:
- %System Root%\autoexec.bat
- %Windows%\ShellNew\sempalong.exe
- %Windows%\BerasJatah.exe
(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)
It does the following:
- Payload 1: Restarts system
- Trigger condition: Upon detection of certain strings in browser window title bar
- Payload 2: Disables Registry Editor and Task Manager
However, as of this writing, the said sites are inaccessible.
SOLUTION
9.850
6.106.04
04 May 2009
6.107.00
04 May 2009
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
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
Restart in Safe Mode
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\sempalong.exe"
- Bron-Spizaetus = "%Windows%\ShellNew\sempalong.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
- DisableCMD = "0"
- DisableCMD = "0"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Tok-Cirrhatus = "%AppDataLocal%\smss.exe"
- Tok-Cirrhatus = "%AppDataLocal%\smss.exe"
Step 5
Restore this modified 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
- From: DisableRegistryTools = "1"
To: DisableRegistryTools = "0"
- From: DisableRegistryTools = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Shell = "Explorer.exe "%Windows%\BerasJatah.exe""
To: Shell = "Explorer.exe"
- From: Shell = "Explorer.exe "%Windows%\BerasJatah.exe""
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
- From: NoFolderOptions = "1"
To: NoFolderOptions = "0"
- From: NoFolderOptions = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: Hidden = "1"
To: Hidden = "0"
- From: Hidden = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: HideFileExt = "1"
To: HideFileExt = "0"
- From: HideFileExt = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: ShowSuperHidden = "0"
To: ShowSuperHidden = "1"
- From: ShowSuperHidden = "0"
Step 6
Search and delete these folders
- %AppDataLocal%\\Bron.tok-{mm}-{dd}
Step 7
Search and delete these files
- %Windows%\ShellNew\sempalong.exe
- %Windows%\BerasJatah.exe
- %AppDataLocal%\smss.exe
- %AppDataLocal%\services.exe
- %AppDataLocal%\lsass.exe
- %AppDataLocal%\inetinfo.exe
- %AppDataLocal%\csrss.exe
- %AppDataLocal%\winlogon.exe
- %System Root%\autoexec.bat
- %User Startup%\Empty.pif
- %Application Data%\Microsoft\Windows\Templates\Brengkolang.com
- %System%\{username}'s Setting.scr
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_RONTKBR.GEN. 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.
Step 9
Scan your computer with your Trend Micro product to delete files detected as WORM_RONTKBR.GEN. 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 the following Trend Micro Support pages for more information:
Did this description help? Tell us how we did.