WORM_BRONTOK.EF
Worm:Win32/Bruhorn.B (Microsoft); W32/Rontokbro.gen@MM (McAfee); Trojan Horse (Symantec); Email-Worm.Win32.Brontok.aa (Kaspersky); Trojan.Win32.Generic.pak!cobra (Sunbelt); Found Luhe.Fiha.A (AVG)
Windows 2000, Windows XP, Windows Server 2003
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.
It disables Task Manager, Registry Editor, and Folder Options.
TECHNICAL DETAILS
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:
- %Application Data%\WINDOWS
- %System Root%\malang
(Note: %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.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
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
4k51k4 = "%Windows%\4k51k4.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
74T1M 3V1L = "%Application Data%\WINDOWS\WINLOGON.EXE"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ServiceAdministrator = "%Application Data%\WINDOWS\SERVICES.EXE"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
LogonAdministrator = "%Application Data%\WINDOWS\CSRSS.EXE"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
System Monitoring = "%Application Data%\WINDOWS\LSASS.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 %System%\IExplorer.exe"
(Note: The default value data of the said registry entry is Explorer.exe.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,%System%\IExplorer.exe"
(Note: The default value data of the said registry entry is %Windows%\system32\userinit.exe,.)
Other System Modifications
This worm deletes the following files:
- %Application Data%\smss.exe
- %Application Data%\csrss.exe
- %Application Data%\winlogon.exe
- %Application Data%\services.exe
- %Application Data%\lsass.exe
- %Temp%\scs2.tmp
- %Temp%\scs8.tmp
- %Temp%\scs1.tmp
- %Temp%\scs6.tmp
- %Temp%\scs3.tmp
- %Temp%\scsA.tmp
- %Temp%\scs4.tmp
- %Temp%\scs5.tmp
- %Temp%\scs7.tmp
- %Temp%\scsC.tmp
- %Temp%\scs9.tmp
- %Temp%\scsD.tmp
- %Temp%\scsB.tmp
- %Temp%\scsE.tmp
- %Temp%\scsF.tmp
- %Temp%\scs11.tmp
- %Temp%\scs10.tmp
- %Temp%\scs12.tmp
- %Temp%\scs13.tmp
- %Temp%\scs16.tmp
- %Temp%\scs14.tmp
- %Temp%\scs18.tmp
- %Temp%\scs15.tmp
- %Temp%\scs1A.tmp
- %Temp%\scs19.tmp
- %Temp%\scs1C.tmp
- %Temp%\scs17.tmp
- %Temp%\scs1B.tmp
- %Temp%\scs1D.tmp
- %Temp%\scs1F.tmp
- %Temp%\scs1E.tmp
- %Temp%\scs23.tmp
- %Temp%\scs21.tmp
- %Temp%\scs24.tmp
- %Temp%\scs20.tmp
- %Temp%\scs25.tmp
- %Temp%\scs22.tmp
- %Temp%\scs26.tmp
- %Temp%\scs28.tmp
- %Temp%\scs2A.tmp
- %Temp%\scs27.tmp
- %Temp%\scs29.tmp
(Note: %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.. %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)
It adds the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\
Control\SafeBoot
HKEY_CLASSES_ROOT\lnkfile\shell\
open\command
HKEY_CURRENT_USER\Software\Policies\
Microsoft\Windows\System
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows NT\SystemRestore
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\
Control\SafeBoot
AlternateShell = "%Windows%\4k51k4.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Window Title = "WANNA START A WAR"
HKEY_CURRENT_USER\Software\Policies\
Microsoft\Windows\System
DisableCMD = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer
NoRun = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows NT\SystemRestore
DisableConfig = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows NT\SystemRestore
DisableSR = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Installer
LimitSystemRestoreCheckpointing = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Installer
DisableMSI = "1"
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\Control Panel\Desktop
SCRNSAVE.EXE = "%System%\MRHALL~1.SCR"
(Note: The default value data of the said registry entry is %Windows%\system32\logon.scr.)
HKEY_CURRENT_USER\Control Panel\Desktop
ScreenSaverIsSecure = "0"
(Note: The default value data of the said registry entry is 0.)
HKEY_CURRENT_USER\Control Panel\Desktop
ScreenSaveTimeOut = "600"
(Note: The default value data of the said registry entry is 600.)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\SafeBoot
AlternateShell = "%Windows%\4k51k4.exe"
(Note: The default value data of the said registry entry is cmd.exe.)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\
Control\SafeBoot
AlternateShell = "%Windows%\4k51k4.exe"
(Note: The default value data of the said registry entry is cmd.exe.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\AeDebug
Debugger = "%System%\Shell.exe"
(Note: The default value data of the said registry entry is "%Program Files%\Microsoft Visual Studio\Common\MSDev98\Bin\msdev.exe" -p %ld -e %ld.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\AeDebug
Auto = "1"
(Note: The default value data of the said registry entry is 0.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
LegalNoticeCaption = "MALANG HACKER"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
LegalNoticeText = "{random characters}"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CabinetState
FullPath = "1"
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 = "0"
(Note: The default value data of the said registry entry is 2.)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
SuperHidden = "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
DisableTaskMgr = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
DisableTaskMgr = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFolderOptions = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer
NoFolderOptions = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFind = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoControlPanel = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
DisableRegistryTools = "1"
Dropping Routine
This worm drops the following files:
- %Common Startup%\Pesan.html
- %System Root%\malang\Folder.htt
- %System Root%\desktop.ini
- %Application Data%\smss.exe
- %Application Data%\csrss.exe
- %Application Data%\winlogon.exe
- %Application Data%\services.exe
- %Application Data%\lsass.exe
- %Windows%\4k51k4.exe
- %System Root%\4k51k4.exe
- %System%\shell.exe
- %System%\MrHallororo.scr
- %System%\IExplorer.exe
- %Common Startup%\MSDOS.pif
- %Application Data%\WINDOWS\WINLOGON.EXE
- %Application Data%\WINDOWS\CSRSS.EXE
- %Application Data%\WINDOWS\SERVICES.EXE
- %Application Data%\WINDOWS\LSASS.EXE
- %Application Data%\WINDOWS\SMSS.EXE
- %System Root%\malang\Malang Hacker.exe
- %System Root%\Data Administrator.exe
(Note: %Common Startup% is the system's shared Startup folder, which is usually C:\Documents and Settings\All Users\Start Menu\Programs\Startup on Windows 2000, XP, and Server 2003.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %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.. %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.)
This report is generated via an automated analysis system.
SOLUTION
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.EF using either the Startup Disk or Recovery Console
Step 3
Enable Registry Editor, Task Manager, and Folder options
Step 4
Delete this registry key
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\ControlSet003\Control
- SafeBoot
- In HKEY_CLASSES_ROOT\lnkfile\shell\open
- command
- In HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows
- System
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies
- System
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies
- Explorer
- In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT
- SystemRestore
Step 5
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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- 4k51k4 = "%Windows%\4k51k4.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- 74T1M 3V1L = "%Application Data%\WINDOWS\WINLOGON.EXE"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- ServiceAdministrator = "%Application Data%\WINDOWS\SERVICES.EXE"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- LogonAdministrator = "%Application Data%\WINDOWS\CSRSS.EXE"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- System Monitoring = "%Application Data%\WINDOWS\LSASS.EXE"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Control\SafeBoot
- AlternateShell = "%Windows%\4k51k4.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- Window Title = "WANNA START A WAR"
- In HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\System
- DisableCMD = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
- NoRun = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\SystemRestore
- DisableConfig = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\SystemRestore
- DisableSR = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Installer
- LimitSystemRestoreCheckpointing = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Installer
- DisableMSI = "1"
- 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 6
Restore these modified registry values
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\Control Panel\Desktop
- From: SCRNSAVE.EXE = "%System%\MRHALL~1.SCR"
To: SCRNSAVE.EXE = ""%Windows%\system32\logon.scr""
- From: SCRNSAVE.EXE = "%System%\MRHALL~1.SCR"
- In HKEY_CURRENT_USER\Control Panel\Desktop
- From: ScreenSaverIsSecure = "0"
To: ScreenSaverIsSecure = ""0""
- From: ScreenSaverIsSecure = "0"
- In HKEY_CURRENT_USER\Control Panel\Desktop
- From: ScreenSaveTimeOut = "600"
To: ScreenSaveTimeOut = ""600""
- From: ScreenSaveTimeOut = "600"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\SafeBoot
- From: AlternateShell = "%Windows%\4k51k4.exe"
To: AlternateShell = ""cmd.exe""
- From: AlternateShell = "%Windows%\4k51k4.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Control\SafeBoot
- From: AlternateShell = "%Windows%\4k51k4.exe"
To: AlternateShell = ""cmd.exe""
- From: AlternateShell = "%Windows%\4k51k4.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug
- From: Debugger = "%System%\Shell.exe"
To: Debugger = """%Program Files%\Microsoft Visual Studio\Common\MSDev98\Bin\msdev.exe" -p %ld -e %ld""
- From: Debugger = "%System%\Shell.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug
- From: Auto = "1"
To: Auto = ""0""
- From: Auto = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- LegalNoticeCaption = "MALANG HACKER"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- LegalNoticeText = "{random characters}"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
- FullPath = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: HideFileExt = "1"
To: HideFileExt = ""1""
- From: HideFileExt = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: Hidden = "0"
To: Hidden = ""2""
- From: Hidden = "0"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- SuperHidden = "0"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Shell = "Explorer.exe %System%\IExplorer.exe"
To: Shell = ""Explorer.exe""
- From: Shell = "Explorer.exe %System%\IExplorer.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Userinit = "%System%\userinit.exe,%System%\IExplorer.exe"
To: Userinit = ""%Windows%\system32\userinit.exe,""
- From: Userinit = "%System%\userinit.exe,%System%\IExplorer.exe"
Step 7
Search and delete these components
- %Common Startup%\Pesan.html
- %System Root%\malang\Folder.htt
- %System Root%\desktop.ini
- %Application Data%\smss.exe
- %Application Data%\csrss.exe
- %Application Data%\winlogon.exe
- %Application Data%\services.exe
- %Application Data%\lsass.exe
- %Windows%\4k51k4.exe
- %System Root%\4k51k4.exe
- %System%\shell.exe
- %System%\MrHallororo.scr
- %System%\IExplorer.exe
- %Common Startup%\MSDOS.pif
- %Application Data%\WINDOWS\WINLOGON.EXE
- %Application Data%\WINDOWS\CSRSS.EXE
- %Application Data%\WINDOWS\SERVICES.EXE
- %Application Data%\WINDOWS\LSASS.EXE
- %Application Data%\WINDOWS\SMSS.EXE
- %System Root%\malang\Malang Hacker.exe
- %System Root%\Data Administrator.exe
Step 8
Search and delete these folders
- %Application Data%\WINDOWS
- %System Root%\malang
Step 9
Scan your computer with your Trend Micro product to delete files detected as WORM_BRONTOK.EF. 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 10
Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.
- %Application Data%\smss.exe
- %Application Data%\csrss.exe
- %Application Data%\winlogon.exe
- %Application Data%\services.exe
- %Application Data%\lsass.exe
- %Temp%\scs2.tmp
- %Temp%\scs8.tmp
- %Temp%\scs1.tmp
- %Temp%\scs6.tmp
- %Temp%\scs3.tmp
- %Temp%\scsA.tmp
- %Temp%\scs4.tmp
- %Temp%\scs5.tmp
- %Temp%\scs7.tmp
- %Temp%\scsC.tmp
- %Temp%\scs9.tmp
- %Temp%\scsD.tmp
- %Temp%\scsB.tmp
- %Temp%\scsE.tmp
- %Temp%\scsF.tmp
- %Temp%\scs11.tmp
- %Temp%\scs10.tmp
- %Temp%\scs12.tmp
- %Temp%\scs13.tmp
- %Temp%\scs16.tmp
- %Temp%\scs14.tmp
- %Temp%\scs18.tmp
- %Temp%\scs15.tmp
- %Temp%\scs1A.tmp
- %Temp%\scs19.tmp
- %Temp%\scs1C.tmp
- %Temp%\scs17.tmp
- %Temp%\scs1B.tmp
- %Temp%\scs1D.tmp
- %Temp%\scs1F.tmp
- %Temp%\scs1E.tmp
- %Temp%\scs23.tmp
- %Temp%\scs21.tmp
- %Temp%\scs24.tmp
- %Temp%\scs20.tmp
- %Temp%\scs25.tmp
- %Temp%\scs22.tmp
- %Temp%\scs26.tmp
- %Temp%\scs28.tmp
- %Temp%\scs2A.tmp
- %Temp%\scs27.tmp
- %Temp%\scs29.tmp
Did this description help? Tell us how we did.