WORM_BRONTOK.DNM
Worm:Win32/Brontok (MICROSOFT); Win32/Brontok.EA worm (NOD32)
Windows 2000, XP, Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This Worm uses the Windows Task Scheduler to add a scheduled task that executes the copies it drops.
It disables Task Manager, Registry Editor, and Folder Options.
TECHNICAL DETAILS
103,047 bytes
EXE
Yes
06 Aug 2018
Installation
This Worm drops the following files:
- %System Root%\autoexec.bat
- %AppDataLocal%\BronNetDomList.bat
- %User Profile%\Pictures\about.Brontok.A.html
(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %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.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista, 7, and 8.)
It drops and executes the following files:
- %AppDataLocal%\inetinfo.exe
- %AppDataLocal%\winlogon.exe
- %AppDataLocal%\smss.exe
- %AppDataLocal%\services.exe
- %AppDataLocal%\lsass.exe
- %AppDataLocal%\csrss.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 drops the following copies of itself into the affected system:
- %Windows%\ShellNew\bronstab.exe
- %Windows%\eksplorasi.pif
- %AppDataLocal%\smss.exe
- %AppDataLocal%\services.exe
- %AppDataLocal%\lsass.exe
- %AppDataLocal%\inetinfo.exe
- %AppDataLocal%\csrss.exe
- %AppDataLocal%\winlogon.exe
- %User Startup%\Empty.pif
- %System%\{username}'s Setting.scr
- %System%\drivers\etc\hosts-Denied By-{username}.com
- %Application Data%\Microsoft\Windows\Templates\WowTumpeh.com
It uses the Windows Task Scheduler to add a scheduled task that executes the copies it drops.
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%\eksplorasi.pif
(Note: The default value data of the said registry entry is explorer.exe.)
The scheduled task executes the malware every:
- 5:08 PM every day
Other System Modifications
This Worm adds the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableCMD = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
AtTaskMaxHours = 48
It modifies the following registry entries:
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.)
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\
Explorer
NoFolderOptions = 1
Propagation
This Worm drops the following copy(ies) of itself in all removable drives:
- {drive letter}:\Data {username}.exe
Process Termination
This Worm terminates the following processes if found running in the affected system's memory:
- mcvsescn.exe
- poproxy.exe
- avgemc.exe
- ccapps.exe
Dropping Routine
This Worm drops the following files:
- %AppDataLocal%\Bron.tok.A8.em.bin
- %AppDataLocal%\Update.8.Bron.Tok.bin
- %AppDataLocal%\Kosong.Bron.Tok.txt
- %AppDataLocal%\BronNPath0.txt
- %AppDataLocal%\ListHost8.txt
- %AppDataLocal%\BronFoldNetDomList.txt
- %AppDataLocal%\Loc.Mail.Bron.Tok\{email}.ini
(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 URL(s) to check for an Internet connection:
- israel.gov.il
- playboy.com
It connects to the following possibly malicious URL:
- http://www.{BLOCKED}ties.com/stabro7ok/BrontokInf8.txt
- http://www.{BLOCKED}ties.com/stabro7ok/Host8.txt
- http://www.{BLOCKED}ies.com/stabro7ok/Bron-ID8.txt
SOLUTION
9.5
14.446.04
16 Aug 2018
14.447.00
17 Aug 2018
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
Enable Registry Editor, Task Manager, and Folder options
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Shell = explorer.exe %Windows%\eksplorasi.pif
To: Shell = explorer.exe
- From: Shell = explorer.exe %Windows%\eksplorasi.pif
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: Hidden = 0
To: Hidden = 1
- From: Hidden = 0
- 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
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
- Tok-Cirrhatus = %Application Data%\smss.exe
- Tok-Cirrhatus = %Application Data%\smss.exe
- 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\Policies\System
- DisableCMD = 0
- DisableCMD = 0
Step 7
Search and delete these files
- %Windows%\ShellNew\bronstab.exe
- %Windows%\eksplorasi.pif
- %AppDataLocal%\smss.exe
- %AppDataLocal%\services.exe
- %AppDataLocal%\lsass.exe
- %AppDataLocal%\inetinfo.exe
- %AppDataLocal%\csrss.exe
- %AppDataLocal%\winlogon.exe
- %User Startup%\Empty.pif
- %System%\{username}'s Setting.scr
- %System%\drivers\etc\hosts-Denied By-{username}.com
- %Application Data%\Microsoft\Windows\Templates\WowTumpeh.com
- %System Root%\autoexec.bat
- %AppDataLocal%\BronNetDomList.bat
- %User Profile%\Pictures\about.Brontok.A.html
- %AppDataLocal%\Bron.tok.A8.em.bin
- %AppDataLocal%\Update.8.Bron.Tok.bin
- %AppDataLocal%\Kosong.Bron.Tok.txt
- %AppDataLocal%\BronNPath0.txt
- %AppDataLocal%\ListHost8.txt
- %AppDataLocal%\BronFoldNetDomList.txt
- %AppDataLocal%\Loc.Mail.Bron.Tok\{email}.ini
- {drive letter}:\Data {username}.exe
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_BRONTOK.DNM. 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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