Analysis by: Paolo Ronniel Labrador
ALIASES:

Trojan.Win64.DLLhijack (IKARUS)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This Ransomware 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 files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size: 139,264 bytes
File Type: DLL
Memory Resident: No
Initial Samples Received Date: 03 Mar 2025
Payload: Displays graphics/image, Drops files, Encrypts files

Arrival Details

This Ransomware 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 Ransomware drops the following files:

  • %ProgramData%\lock.log → logs the success and failure of file encryptions

(Note: %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\lockv7

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html = %ProgramData%\unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html = %ProgramData%\unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html

Other Details

This Ransomware does the following:

  • It is loaded by the following file:
    • usysdiag.exe → signed legitimate executable
  • It decrypts its code from the following file:
    • usysdiag.exe.dat → contains encrypted payload

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file name:

  • boot.ini
  • unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html

It avoids encrypting files found in the following folders:

  • Boot
  • Windows
  • Program Files
  • Program Files (x86)
  • ProgramData
  • AppData
  • Application Data

It appends the following extension to the file name of the encrypted files:

  • .locked

It drops the following file(s) as ransom note:

  • {encrypted path}\unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html
  • %ProgramData%\unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html

It avoids encrypting files with the following file extensions:

  • .exe
  • .dll
  • .sys
  • .locked

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 19.936.03
FIRST VSAPI PATTERN DATE: 03 Mar 2025
VSAPI OPR PATTERN File: 19.937.00
VSAPI OPR PATTERN Date: 04 Mar 2025

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

    • TROJ.Win32.TRX.XXPE50FFF091

Step 2

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 3

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 4

Restart in Safe Mode

[ Learn More ]

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\Microsoft\Windows\CurrentVersion\Run
    • unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html = %ProgramData%\unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html

Step 6

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.
  • %ProgramData%\lock.log
  • {encrypted path}\unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html
  • %ProgramData%\unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please_view_this_file_unlock_please.html
  • usysdiag.exe.dat
  • usysdiag.exe

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win64.LAONAI.THCOCBE. 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.

Step 8

Restore encrypted files from backup.


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