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Trojan.Win64.PATCHED.A

December 14, 2022
 Analysis by: Ricardo III Valdez
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Via app stores

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

It connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

886,784 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

02 Dec 2022

Payload:

Connects to URLs/IPs, Drops files

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %User Temp%\offscan.bat ← Creates and runs a scheduled task
  • %Windows%\Trend Micro\Security Center\fcwolfui.dll ← Dropped copy

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It adds the following processes:

  • cmd /c schtasks /create /f /ru SYSTEM /tn "Trend Micro\Security Center\OfficeScan Agent" /sc ONSTART /tr rundll32.exe "%Windows%\Trend Micro\Security Center\fcwolfui.dll",SHGetAgent
  • cmd /c schtasks /Run /tn Trend Micro\Security Center\OfficeScan Agent
  • del /f %User Temp%\offscan.bat

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It creates the following folders:

  • %Windows%\Trend Micro
  • %Windows%\Trend Micro\Security Center
  • %ProgramData%\Intel
  • %ProgramData%\Intel\DAL

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.)

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

  • Global\TM-a100

Other Details

This Trojan connects to the following website to send and receive information:

  • http://css.{BLOCKED}ess.com

It does the following:

  • It checks if it is executed using rundll32.exe
    • If Yes, it proceeds to its payload (Connects to a URL/IP)
    • If No, it creates a scheduled task (Using offscan.bat)

  • It attempts to rename itself to the following:
    • {Malware File Path}\{8 Random Characters}.tmp
      If renaming is successful, it will delete the file after system reboot

However, as of this writing, the said sites are inaccessible.

It adds the following scheduled tasks:

  • Task Name: OfficeScan Agent
    Trigger: At system startup
    Task to be Run: rundll32.exe "%Windows%\Trend Micro\Security Center\fcwolfui.dll",SHGetAgent

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.112.04

FIRST VSAPI PATTERN DATE:

04 Dec 2022

VSAPI OPR PATTERN File:

18.113.00

VSAPI OPR PATTERN Date:

05 Dec 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

Deleting Scheduled Tasks while in Safe Mode

  1. Still in safe mode, the following {Task Name}-{Task to be run} listed should be used in the steps identified below:

    • Task Name: OfficeScan Agent
      Task to be run: rundll32.exe %Windows%\Trend Micro\Security Center\fcwolfui.dll,SHGetAgent

  2. For Windows 7 and Server 2008 (R2) users, click Start>Computer.
    • For Windows 8, 8.1, 10, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
  3. In the Search Computer/This PC input box, type:
    • %System%\Tasks\{Task Name}
  4. Once located, select the file then press SHIFT+DELETE to delete it.
  5. Open Registry Editor. To do this:
    • For Windows 7 and Server 2008 (R2) users, click the Start button, type regedit in the Search input field, and press Enter.
    • For Windows 8, 8.1, 10, and Server 2012 (R2) users, right-click on the lower left corner of the screen, click Run, type regedit in the text box
  6. In the left panel of the Registry Editor window, double-click the following:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
  7. Locate the created entry and take note of the registry value's data:
    • ID={Task Data}
  8. After taking note of the data, delete the registry key:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
  9. In the left panel of the Registry Editor window, double-click the following:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tasks
  10. Still in the left panel, locate and delete the registry key with the same name as the located Task Data in step #6:
    • ={Task Data}
  11. Close Registry Editor.

Step 5

Search and delete these files

[ 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.
  • %User Temp%\offscan.bat
  • %Windows%\Trend Micro\Security Center\fcwolfui.dll

Step 6

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.
  • %Windows%\Trend Micro\Security Center
  • %Windows%\Trend Micro
  • %ProgramData%\Intel\DAL
  • %ProgramData%\Intel

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.Win64.PATCHED.A. 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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