BKDR_PLUGX.BT

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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

It deletes itself after execution.

Arrival Details

This backdoor 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 backdoor creates the following folders:

• %User Temp%\RarSFX0
• %All Users Profile%\SxS

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

It stays memory-resident by injecting codes into the following processes:

• svchost.exe

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS
ImagePath = "%All Users Profile%\SxS\Nv.exe" 200 0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS
DisplayName = "SxS"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS
Description = "SxS"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SXS

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS\Security

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SxS\Enum

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CLASSES_ROOT\FAST

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Setttings\
5.0\User Agent

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Setttings\
5.0\User Agent\Post Platform

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Setttings\
User Agent

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Setttings\
User Agent\Post Platform

HKEY_LOCAL_MACHINE\FAST

It adds the following registry entries:

HKEY_CLASSES_ROOT\FAST
CLSID = "{random hex values}"

HKEY_LOCAL_MACHINE\FAST
CLSID = "{random hex values}"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

• Copy, move, rename, delete files
• Create directories
• Create files
• Enumerate files
• Execute files
• Get drive information
• Get file information
• Open and modify files
• Log keystrokes and active window
• Enumerate TCP and UDP connections
• Enumerate network resources
• Set TCP connection state
• Lock workstation
• Log off user
• Restart/Reboot/Shutdown system
• Display a message box
• Perfrom port mapping
• Enumerate processes
• Get process information
• Terminate processes
• Enumerate registry keys
• Create registry keys
• Delete registry keys
• Copy registry keys
• Enumerate registry entries
• Modify registry entries
• Delete registry values
• Screen capture
• Delete services
• Enumerate services
• Get service information
• Modify services
• Start services
• Perform remote shell
• Connect to a database server and execute SQL statement
• Host Telnet server

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

• {BLOCKED}afes.no-ip.org
• {BLOCKED}i.ns01.us/update?id={id}

Dropping Routine

This backdoor drops the following files:

• %User Temp%\RarSFX0\Nv.abc
• %User Temp%\RarSFX0\NvSmartMax.dll - also detected as BKDR_PLUGX.BT
• %User Temp%\RarSFX0\Nv.exe - deleted afterwards
• %All Users Profile%\SxS\Nv.abc
• %All Users Profile%\SxS\NvSmartMax.dll - also detected as BKDR_PLUGX.BT
• %All Users Profile%\SxS\Nv.exe
• %All Users Profile%\SxS\bug.log

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

Other Details

This backdoor deletes itself after execution.