BKDR_PLUGX.BT

 Modified by: Jimelle Monteser

 ALIASES:

Backdoor.Korplug (Norton), Backdoor.Win32.Gulpix (Ikarus), Win32/Korplug.AT trojan (NOD32)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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.

  TECHNICAL DETAILS

File Size:

251,282 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

20 Feb 2014

Payload:

Compromises system security, Connects to URLs/IPs, Drops files

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.

  SOLUTION

Minimum Scan Engine:

9.700

VSAPI OPR PATTERN File:

10.617.00

VSAPI OPR PATTERN Date:

20 Feb 2014

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry key

[ 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\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_SXS
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • SxS
  • In HKEY_CLASSES_ROOT
    • FAST
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Setttings\5.0
    • User Agent
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Setttings
    • User Agent
  • In HKEY_LOCAL_MACHINE
    • FAST

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\RarSFX0
  • %All Users Profile%\SxS

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_PLUGX.BT. 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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