Backdoor.Win32.PLUGX.EYSGVW


 ALIASES:

Trojan:Win32/Korplug!MSR

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware, Propagates via flashdrives

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 drops copies of itself in all removable drives.

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

  TECHNICAL DETAILS

File Size:

159,833 bytes

File Type:

ZIP

File Compression:

ZIP

Memory Resident:

Yes

Initial Samples Received Date:

29 Mar 2023

Payload:

Drops files, Collects system information, Connects to URLs/IPs, Terminates processes, Deletes 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 adds the following folders:

  • %All Users Profile%\AvastSvcyHA → if it executes without a {random numbers} in the commandline
  • {Drive}\RECYCLER.BIN
  • {Drive}\RECYCLER.BIN\1
  • {Drive}\RECYCLER.BIN\{RANDOM}
  • %Application Data%\Intel

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). . %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It drops the following files:

  • %All Users Profile%\AvastSvcyHA\AvastSvc.exe→ if it executes without {random numbers} in the commandline
  • %All Users Profile%\AvastSvcyHA\wsc.dll→ if it executes without {random numbers} in the commandline
  • %All Users Profile%\AvastSvcyHA\AvastAuth.dat → if it executes without {random numbers} in the commandline

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

It adds the following processes:

  • %All Users Profile%\AvastSvcyHA\AvastSvc.exe {Random Numbers} → if it executes without {random numbers} in the commandline

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • GJsgXZYVrgqcUMNVXzvU
  • USB_NOTIFY_INF_{Drive}
  • USB_NOTIFY_COP_{Drive}

Autostart Technique

This Backdoor modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
AvastSvcyHA = "%All Users Profile%\AvastSvcyHA\AvastSvc.exe" {Random Numbers} → if it executes without {random numbers} in the commandline

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
AvastSvcyHA = "%All Users Profile%\AvastSvcyHA\AvastSvc.exe" {Random Numbers} → if it executes without {random numbers} in the commandline

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
ms-pu
CLSID = {hex values}

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Network
Version = 1 → if commandline is -net

HKEY_CURRENT_USER\System\CurrentControlSet\
Control\Network
Version = 1 → if commandline is -net

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 0

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

Propagation

This Backdoor drops copies of itself in all removable drives.

It creates shortcut files (.LNK) disguised as folders or files located on the affected drives pointing to the malware copy.

Backdoor Routine

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

  • Get system information
  • Start pipe communication
  • Echo back given input
  • Exit process
  • Get disk information
  • Manage file (query, read, write, delete, copy, rename, move)
  • Create directory
  • Get expanded environment variable
  • Get malware directory
  • Execute arbitrary command

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

  • {BLOCKED}.{BLOCKED}.226.100

Process Termination

This Backdoor terminates the following processes if found running in the affected system's memory:

  • AdobeHelper.exe
  • AdobeUpdates.exe
  • AdobeUpdate.exe
  • AdobeARM.exe
  • AAM Update.exe
  • AAM Updates.exe

Information Theft

Upon execution of the affected application, it gathers the following information:

  • Results of the following commands:
    • systeminfo (Details about the operating system and the system hardware and software components)
    • ipconfig (Details about current TCP/IP network configuration)
    • netstat (Details about current TCP connections)
    • arp (Details about local ARP cache)
    • tasklist (Details about running processes)

It accepts the following parameters:

  • -net → set the value of key registry “System\CurrentControlSet\Control\Network\Version” to “1”

Other Details

This Backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
ms-pu

HKEY_USER\{SID}_CLASSES\ms-pu

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
ms-pu\PROXY

It connects to the following URL(s) to check for an Internet connection:

  • https://www.microsoft.com

It does the following:

  • It deletes all files found in the folder of the terminated process.
  • It deletes the folder of the terminated process.
  • It modifies {Drive}\RECYCLER.BIN to point to the system's Recycle Bin
  • It drops the following files inside {Drive}\RECYCLER.BIN\1:
    • CEFHelper.exe (Copy of the parent executable that loaded the malware)
    • wsc.dll (Copy of the malware)
    • AvastAuth.dat (Copy of the encrypted component needed to execute the malware)
  • It drops the following files inside {Drive}\RECYCLER.BIN\{RANDOM}:
    • tmp.bat (Contains commands to query system information)
    • c3lzLmluZm8 (Contains results of queried system information)
    • {Base64-Encoded Filenames} (Encrypted version of files with the extensions .doc, .docx, .ppt, .pptx, .xls, .xlsx, .pdf)
  • It hides the normal counterpart of the malicious shortcut files created in the removable drives.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.364.02

FIRST VSAPI PATTERN DATE:

05 Apr 2023

VSAPI OPR PATTERN File:

18.365.00

VSAPI OPR PATTERN Date:

06 Apr 2023

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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

Identify and terminate files detected as Backdoor.Win32.PLUGX.EYSGVW

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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\Classes\ms-pu
    • CLSID = {Hex Values}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • AvastSvcyHA =  %AllUsersProfile%\AvastSvcyHA\AvastSvc.exe {Random Numbers}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • AvastSvcyHA = %AllUsersProfile%\AvastSvcyHA\AvastSvc.exe  {Random Numbers}
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Network
    • Version = 1
  • In HKEY_CURRENT_USER\System\CurrentControlSet\Control\Network
    • Version = 1

Step 6

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\SOFTWARE\Classes\ms-pu
  • In HKEY_USER\{SID}_CLASSES\ms-pu
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\ms-pu\PROXY

Step 7

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 = 0
    • To Hidden = {Default value}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From ShowSuperHidden = 0
    • To ShowSuperHidden = {Default value}

Step 8

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.
  • %All Users Profile%\AvastSvcyHA\AvastSvc.exe
  • %All Users Profile%\AvastSvcyHA\wsc.dll
  • %All Users Profile%\AvastSvcyHA\AvastAuth.dat
  • Files Inside {Drive}\RECYCLER.BIN

Step 9

Search and delete this folder

[ 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.
  • %All Users Profile%\AvastSvcyHA
  • {Drive}\RECYCLER.BIN
  • %Application Data%\Intel

Step 10

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.PLUGX.EYSGVW. 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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