Backdoor.Win32.SHADOWPAD.RJACGZ

March 23, 2022
 Analysis by: Mc Justine De Guzman
 ALIASES:

a variant of Win32/Shadowpad.T trojan (NOD32)

 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

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.

  TECHNICAL DETAILS

File Size:

1,668,096 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

22 Mar 2022

Payload:

Modifies system registry, Drops files, Executes files, Others, Connects to URLs/IPs

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%\Temp\smss.exe → loads mscoree.dll
  • %All Users Profile%\Temp\mscoree.dll → detected as Backdoor.Win32.SHADOWPAD.RJACGZ (loads mscoree.dll.mui)
  • %All Users Profile%\Temp\mscoree.dll.mui → detected as Backdoor.Win32.SHADOWPAD.RJACGZ (main routine)

(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:

  • If its execution path is %All User Profile%\Temp:
    • %All Users Profile%\Temp\smss.exe
    • %Program Files%\Windows Media Player\wmplayer.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It creates the following folders:

  • %All Users Profile%\Temp

(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:

  • Global\{Random numbers}

It injects codes into the following process(es):

  • %Program Files%\Windows Media Player\wmplayer.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
smss = %All Users Profile%\Temp\smss.exe

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\gft
gft = {Hex Values}

Backdoor Routine

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

  • Download and execute arbitrary codes

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

  • https://offine.{BLOCKED}p.com:443
  • http://offine.{BLOCKED}p.com:8080
  • http://offine.{BLOCKED}p.com:80

As of this writing, the said servers are currently inaccessible.

Other Details

This Backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\gft

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PxBbzdfvzb

It requires the following additional components to properly run:

  • %All Users Profile%\Temp\mscoree.dll.mui → detected as Backdoor.Win32.SHADOWPAD.RJACGZ

(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 and runs the following services:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\smss
ImagePath = %All Users Profile%\Temp\smss

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

17.416.06

FIRST VSAPI PATTERN DATE:

02 Mar 2022

VSAPI OPR PATTERN File:

17.417.00

VSAPI OPR PATTERN Date:

03 Mar 2022

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

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\Microsoft\Windows\CurrentVersion\Run
    • smss = %All Users Profile%\Temp\smss.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\gft
    • gft = {Hex Values}

Step 5

Disable this malware service

[ Learn More ]
    • smss

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\gft
    • = ""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PxBbzdfvzb
    • = ""

Step 7

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%\Temp\smss.exe
  • %All Users Profile%\Temp\mscoree.dll
  • %All Users Profile%\Temp\mscoree.dll.mui

Step 8

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.
  • %All Users Profile%\Temp

Step 9

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