PE_MOFKSYS.A

This file infector 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 Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It modifies registry entries to disable various system services. This action prevents most of the system functions to be used.

It prepends its codes to target files.

It executes commands from a remote malicious user, effectively compromising the affected system.

It steals certain information from the system and/or the user.

Arrival Details

This file infector 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 file infector drops the following non-malicious files:

• %System%\cmsys.cmn
• %User Profile%\Application Data\icsys.icn

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.. %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.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Autostart Technique

This file infector adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
Svchost = "%Windows%\svchost.exe RO"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{Random CLSID}
StubPath = "%Application Data%\mrsys.exe MR"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
Explorer = "%System%\explorer.exe RO"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Explorer = "%System%\explorer.exe RU"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Svchost = "%Windows%\svchost.exe RU"

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 = "%Windows%\explorer.exe, %System%\explorer.exe"

(Note: The default value data of the said registry entry is Explorer.exe.)

The scheduled task executes the malware at the following period:

• Everyday at malware's first execution time

Other System Modifications

This file infector adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
Explorer\Process
LO = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
AtTaskMaxHours = "48"

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\VB and VBA Program Settings

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
Explorer

HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
Explorer\Process

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{Random CLSID}

It modifies registry entries to disable the following system services:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess
Start = "4"

(Note: The default value data of the said registry entry is 2.)

It modifies the following registry entries to hide files with Hidden attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

(Note: The default value data of the said registry entry is 1.)

File Infection

This file infector infects the following file types:

• .EXE

It prepends its codes to target files.

This is the Trend Micro detection for files infected by:

• PE_MOFKSYS.A-O

Backdoor Routine

This file infector executes the following commands from a remote malicious user:

• Update itself
• Download other files
• Capture screen
• Log Keystrokes
• Monitor mouse clicks
• Monitor window titles

It connects to the following URL(s) to send and receive commands from a remote malicious user:

• {BLOCKED}.t35.com
• {BLOCKED}.atspace.com
• {BLOCKED}.zxq.net

Dropping Routine

This file infector drops the following files:

• %Application Data%\mrsys.exe - detected as PE_MOFKSYS.A-O
• %Windows%\spoolsv.exe - detected as PE_MOFKSYS.A-O
• %Windows%\svchost.exe - detected as PE_MOFKSYS.A-O
• %System%\explorer.exe - detected as PE_MOFKSYS.A-O
• %User Profile%\Application Data\icsys.icn.exe - detected as PE_MOFKSYS.A-O
• %System Root%\Documents and Settings\All Users\Application Data\stsys.exe - detected as PE_MOFKSYS.A-O

(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.. %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.. %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.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Information Theft

This file infector steals the following information:

• Email configurations
• - User name
• - Password
• - Authenticate status
• - Use of SSL
• - SMTP server
• - SMTP port
• - recipients
• Instant messenger credentials
• Websites visited
• Clipboard contents

Drop Points

This file infector uses its own SMTP engine to send the stolen data using the following domain server:

• {BLOCKED}1@gmail.com
• {BLOCKED}1@gmail.com
• {BLOCKED}2@gmail.com
• {BLOCKED}2@gmail.com
• {BLOCKED}6@gmail.com

NOTES:

It infects all .EXE files inside the folders that was accessed by the user in all physical and removable drives.

It also shares the following folder in the network:

• %System Root%\Documents and Settings\All User\Application Data