BKDR_PLUGX.BIN

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 does not have any propagation routine.

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

It deletes the initially executed copy of itself.

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 drops the following files:

• %All Users Profile%\DRM\vncutil\vncutil.exe - normal file used to load vncutilLOC.dll
• %All Users Profile%\DRM\vncutil\vncutilLOC.dll - copy of itself, detected as BKDR_PLUGX.BIN

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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 adds the following processes:

• svchost.exe

It creates the following folders:

• %All Users Profile%\DRM\vncutil

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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 adds the following mutexes to ensure that only one of its copies runs at any one time:

• My_Name1

It injects codes into the following process(es):

• created svchost.exe

Autostart Technique

This backdoor 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\
Services\vncutil

It registers its dropped component as a system service to ensure its automatic execution at every system startup. It does this by creating the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\vncutil
ImagePath = "%All Users Profile%\DRM\vncutil\vncutil.exe"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\vncutil
Description = "Noise Canceling Program"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\vncutil
Type = "272"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\BINARY
vncutil = "{hex values}" - config data

HKEY_LOCAL_MACHINE\SOFTWARE\BINARY
vncutil = "{hex values}" - config data

Propagation

This backdoor does not have any propagation routine.

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
• Host Telnet server
• Connect to a database server and execute SQL statement

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

• http://{BLOCKED}l.naengmyeon.net:443/{random values}

As of this writing, the said sites are inaccessible.

Dropping Routine

This backdoor drops the following files:

• %All Users Profile%\DRM\vncutil\{random file name 1} - encrypted data
• %All Users Profile%\DRM\vncutil\{random file name 2} - encrypted data

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.)

Other Details

This backdoor deletes the initially executed copy of itself

NOTES:

If the “%All Users Profile%\DRM” folder is not present in the affected machine, it will drop its files in:

• “%All Users Profile%\vncutil\” (for Windows XP and below)
• “%Program Data%\vncutil” (for Windows Vista and above)