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WORM_BRONTOK.MFT

March 23, 2015
 Analysis by: Francis Xavier Antazo
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Spammed via email, Downloaded from the Internet

This worm arrives as attachment to mass-mailed email messages. It arrives via removable drives. 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.

It drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

Arrival Details

This worm arrives as attachment to mass-mailed email messages.

It arrives via removable drives.

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 and executes them:

  • %AppDataLocal%\smss.exe
  • %AppDataLocal%\services.exe
  • %AppDataLocal%\lsass.exe
  • %AppDataLocal%\inetinfo.exe
  • %AppDataLocal%\csrss.exe
  • %AppDataLocal%\svchost.exe
  • %AppDataLocal%\winlogon.exe

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following files:

  • %AppDataLocal%\BronMes{random characters}.ini
  • %System%\system32\sistem.sys

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It drops the following copies of itself into the affected system:

  • %User Profile%\Local Settings\Application Data\br{random characters}on.exe
  • %User Profile%\Templates\{random 5 characters}-NendangBro.com
  • %System%\(username)'s Setting.scr
  • %System%\DXBLCI.exe
  • %System%\cmd-bro-{random 3 characters}.exe
  • %Windows%\SHELLNEW\bbm-{random 8 characters}.exe
  • %Windows%\sembako-{random 7 characters}.exe

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_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Bron-Spizaetus-{random 8 characters} = "%System%\ShellNew\bbm-{random 8 characters}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Tok-Cirrhatus-{random 4 characters} = "%AppDataLocal%\br{random characters}on.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe "%System%\sembako-{random 7 characters}.exe""

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot
AlternateShell = "cmd-bro-{random 3 characters}.exe"

The scheduled task executes the malware every:

  • 5:08 PM
  • 11:03 AM

It enables its automatic execution at every system startup by dropping the following copies of itself into the Windows Common Startup folder:

  • %User Profile%\Start Menu\Programs\Startup\Empty.pif

(Note: %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 and 7.)

Other System Modifications

This worm adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableCMD = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFolderOptions = "1"

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".)

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • {Removable Drive Letter}:\Data {username}.exe

It drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

It gathers target email addresses from files with the following extensions:

  • .HTM
  • .HTML
  • .TXT
  • .EML
  • .WAB
  • .ASP
  • .PHP
  • .CFM
  • .CSV
  • .DOC

It avoids sending email messages to addresses containing the following strings:

  • SECURE
  • SUPPORT
  • MASTER
  • MICROSOFT
  • VIRUS
  • HACK
  • CRACK
  • LINUX
  • AVG
  • GRISOFT
  • CILLIN
  • SECURITY
  • SYMANTEC
  • ASSOCIATE
  • VAKSIN
  • NORTON
  • NORMAN
  • PANDA
  • SOFT
  • SPAM
  • BLAH
  • YOUR
  • SOME
  • ASDF
  • @.
  • .@
  • WWW
  • VAKSIN
  • DEVELOP
  • PROGRAM
  • SOURCE
  • NETWORK
  • UPDATE
  • TEST
  • ..
  • XXX
  • SMTP
  • EXAMPLE
  • CONTOH
  • INFO@
  • BILLING@
  • .ASP
  • .PHP
  • .HTM
  • .EXE
  • .JS
  • .VBS
  • DOMAIN
  • HIDDEN
  • DEMO
  • DEVELOP
  • FOO@
  • KOMPUTER
  • SENIOR
  • DARK
  • BLACK
  • BLEEP
  • FEEDBACK
  • IBM.
  • INTEL.
  • MACRO
  • ADOBE
  • FUCK
  • RECIPIENT
  • SERVER
  • PROXY
  • ZEND
  • ZDNET
  • CNET
  • DOWNLOAD
  • HP.
  • XEROX
  • CANON
  • SERVICE
  • ARCHIEVE
  • NETSCAPE
  • MOZILLA
  • OPERA
  • NOVELL
  • NEWS
  • UPDATE
  • RESPONSE
  • OVERTURE
  • GROUP
  • GATEWAY
  • RELAY
  • ALERT
  • SEKUR
  • CISCO
  • LOTUS
  • MICRO
  • TREND
  • SIEMENS
  • FUJITSU
  • NOKIA
  • W3.
  • NVIDIA
  • APACHE
  • MYSQL
  • POSTGRE
  • SUN.
  • GOOGLE
  • SPERSKY
  • ZOMBIE
  • ADMIN
  • AVIRA
  • AVAST
  • TRUST
  • ESAVE
  • ESAFE
  • PROTECT
  • ALADDIN
  • ALERT
  • BUILDER
  • DATABASE
  • AHNLAB
  • PROLAND
  • ESCAN
  • HAURI
  • NOD32
  • SYBARI
  • ANTIGEN
  • ROBOT
  • ALWIL
  • BROWSE
  • COMPUSE
  • COMPUTE
  • SECUN
  • SPYW
  • REGIST
  • FREE
  • BUG
  • MATH
  • LAB
  • IEEE
  • KDE
  • TRACK
  • INFORMA
  • FUJI
  • @MAC
  • SLACK
  • REDHA
  • SUSE
  • BUNTU
  • XANDROS
  • @ABC
  • @123
  • LOOKSMART
  • SYNDICAT
  • ELEKTRO
  • ELECTRO
  • NASA
  • LUCENT
  • TELECOM
  • STUDIO
  • SIERRA
  • USERNAME
  • IPTEK
  • CLICK
  • SALES
  • PROMO

Download Routine

As of this writing, the said sites are inaccessible.

Other Details

This worm terminates itself if windows or classes contain any of the following string(s):

  • REGISTRY
  • SYSTEM CONFIGURATION
  • COMMAND PROMPT
  • .EXE
  • SHUTDOWN
  • SCRIPT HOST
  • LOG OFF WINDOWS
  • KILLBOX
  • TASK KILL
  • TASKKILL
  • HIJACK
  • BLEEPING
  • SYSINTERNAL
  • PROCESS EXP
  • FAJARWEB
  • REMOVER
  • CLEANER
  • GROUP POLICY
  • MOVZX

NOTES:

It tries to download from the following URLs:

  • http://www.{BLOCKED}b.com/Kids/{random characters}/{random characters}.css

It pings for the following URLs:

  • http://www.{BLOCKED}n.com
  • http://www.{BLOCKED}s.com
  • http://www.{BLOCKED}eb.com

This worm restarts the system if the following strings are present in an existing window:

  • REGISTRY
  • SYSTEM CONFIGURATION
  • COMMAND PROMPT
  • .EXE
  • SHUTDOWN
  • SCRIPT HOST
  • LOG OFF WINDOWS
  • KILLBOX
  • TASK KILL
  • TASKKILL
  • HIJACK
  • BLEEPING
  • SYSINTERNAL
  • PROCESS EXP
  • FAJARWEB
  • REMOVER
  • CLEANER
  • GROUP POLICY
  • MOVZX

  SOLUTION

Minimum Scan Engine:

9.750

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

[ Learn More ]

Step 4

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Profile%\Start Menu\Programs\Startup\Empty.pif
  • %User Profile%\Templates\{random 5 characters}-NendangBro.com
  • %User Profile%\Local Settings\Application Data\BronMes{long random characters}.ini
  • %System%\system32\sistem.sys

Step 5

Delete this registry value

[ Learn More ]

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-{random 8 characters} = "%System%\ShellNew\bbm-{random 8 characters}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Tok-Cirrhatus-{random 4 characters} = "%AppDataLocal%\br{random characters}on.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Shell = "Explorer.exe "%System%\sembako-{random 7 characters}.exe""
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot
    • AlternateShell = "cmd-bro-{random 3 characters}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableCMD = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableRegistryTools = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoFolderOptions = "1"

Step 6

Restore this modified registry value

[ Learn More ]

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\Explorer\Advanced
    • From: Hidden = "1"
      To: Hidden = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "0"
      To: HideFileExt = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "1"
      To: ShowSuperHidden = "0"

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_BRONTOK.MFT. 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 8

Scan your computer with your Trend Micro product to delete files detected as WORM_BRONTOK.MFT. 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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