WORM_BRONTOK.FL
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
Propagates via removable drives
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 drops copies of itself into all the removable drives connected to an affected system.
TECHNICAL DETAILS
1,006,592 bytes
EXE
No
09 Feb 2011
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 drops the following copies of itself into the affected system:
- %System Root%\AUT0EXEC.BAT
- %Windows%\system32.exe
- %System%\dllchache\Blank.doc
- %System%\dllchache\Empty.jpg
- %System%\dllchache\Hole.zip
- %System%\dllchache\Unoccupied.reg
- %System%\dllchache\Zero.txt
- %System%\M5VBVM60.EXE
- %System%\dllcache\Regedit32.com
- %System%\dllcache\Shell32.com
- %System%\dllchache\Empty.jpg
It drops the following files:
- %System Root%\(Read Me)Pendekar Blank.txt
- %System Root%\msvbvm60.dll
- %System%\dllchache\msvbvm60.dll
- %System%\dllchache.exe
- %System%\rund1132.exe
- %System%\dllcache\msvbvm60.dll
- %System%\drivers\iopfqo.sys
- %Current Folder%\{malware name}
- %System%\mm304929.dll
- %System%\mm304929.dl_
- %System%\mm304929.dll
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %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.)
It creates the following folders:
- %System%\dllchache
(Note: %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.)
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
Secure64 = %System%\dllcache\Regedit32.com StartUp
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Secure32 = %System%\dllcache\Shell32.com StartUp
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Blank AntiViri = %System Root%\AUT0EXEC.BAT StartUp
Other System Modifications
This worm adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLUA = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
\??\%system%\winlogon.exe = \??\%system%\winlogon.exe:*:enabled:@shell32.dll,-1
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot
AlternateShell = %System Root%\AUT0EXEC.BAT StartUp
(Note: The default value data of the said registry entry is cmd.exe.)
Propagation
This worm drops copies of itself into all the removable drives connected to an affected system.
SOLUTION
8.900
7.824.01
09 Feb 2011
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
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
- Secure64 = %System%\dllcache\Regedit32.com StartUp
- Secure64 = %System%\dllcache\Regedit32.com StartUp
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Secure32 = %System%\dllcache\Shell32.com StartUp
- Secure32 = %System%\dllcache\Shell32.com StartUp
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- Blank AntiViri = %System Root%\AUT0EXEC.BAT StartUp
- Blank AntiViri = %System Root%\AUT0EXEC.BAT StartUp
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
- EnableLUA = 0
- EnableLUA = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- \??\%System%\winlogon.exe = \??\%System%\winlogon.exe:*:enabled:@shell32.dll,-1
- \??\%System%\winlogon.exe = \??\%System%\winlogon.exe:*:enabled:@shell32.dll,-1
Step 3
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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot
- From: AlternateShell = %System Root%\AUT0EXEC.BAT StartUp
- To: AlternateShell = cmd.exe
Step 4
Search and delete these folders
Step 5
Search and delete this file
Step 6
Scan your computer with your Trend Micro product to delete files detected as WORM_BRONTOK.FL. 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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