Analysis by: Thea Patrice Tajonera
ALIASES:

Trojan-Ransom.FileCrypter (IKARUS)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

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.

  TECHNICAL DETAILS

File Size: 1,102,848 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 02 Jul 2021
Payload: Displays message/message boxes, Encrypts files, Steals information

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:

  • %User Temp%\tmp.ini -> deleted afterwards

(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).)

It adds the following processes:

  • %System%\cmd.exe /c taskkill.exe /IM sqlservr.exe /F
  • %System%\cmd.exe /c REG ADD "HKEY_USERS\.DEFAULT\Control Panel\Desktop" /V Wallpaper /T REG_SZ /F /D "%ProgramW6432%\Lorenz.bmp"
  • %System%\cmd.exe /c REG ADD "HKEY_USERS\S-1-5-19\Control Panel\Desktop" /V Wallpaper /T REG_SZ /F /D "%ProgramW6432%\Lorenz.bmp"
  • %System%\cmd.exe /c REG ADD "HKEY_USERS\S-1-5-20\Control Panel\Desktop" /V Wallpaper /T REG_SZ /F /D "%ProgramW6432%\Lorenz.bmp"
  • %System%\cmd.exe /c REG ADD "HKEY_USERS\S-1-5-21-2019512041-4230814187-3178073052-1000\Control Panel\Desktop" /V Wallpaper /T REG_SZ /F /D "%ProgramW6432%\Lorenz.bmp"
  • %System%\cmd.exe /c REG ADD "HKEY_USERS\S-1-5-21-2019512041-4230814187-3178073052-1000_Classes\Control Panel\Desktop" /V Wallpaper /T REG_SZ /F /D "%ProgramW6432%\Lorenz.bmp"
  • %System%\cmd.exe /c REG ADD "HKEY_USERS\S-1-5-18\Control Panel\Desktop" /V Wallpaper /T REG_SZ /F /D "%ProgramW6432%\Lorenz.bmp"
  • %System%\cmd.exe /c shutdown -t 1 -r

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

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

  • corp-{Organization Name}

Information Theft

This Ransomware gathers the following data:

  • Computer Name

Other Details

This Ransomware does the following:

  • It send the stolen information to the following URL:
    • {BLOCKED}.{BLOCKED}.75.63
  • This Ransomware encrypts the following drives:
    • Fixed Drives
    • Removable Drives
    • Remote (Network) Drives
  • It changes the desktop wallpaper
  • It restarts the affected machine after encrypting

Ransomware Routine

This Ransomware avoids encrypting files found in the following folders:

  • Program Files
  • AppData
  • WINDOWS
  • Windows
  • $Recycle.Bin
  • Local
  • All Users
  • Packages
  • Microsoft

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

  • {Original Filename}.{Original Extension}.Lorenz.sz40

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

  • {Encrypted Drive}\HELP_SECURITY_EVENT.html
  • %Desktop%\HELP_SECURITY_EVENT.html

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.886.03
FIRST VSAPI PATTERN DATE: 05 Aug 2021
VSAPI OPR PATTERN File: 16.887.00
VSAPI OPR PATTERN Date: 06 Aug 2021

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.XXPE50FFF046

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

Reset your Desktop properties

[ Learn More ]

Step 5

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.
  • {Encrypted Drive}\HELP_SECURITY_EVENT.html
  • %Desktop%\HELP_SECURITY_EVENT.html

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.THUNDERCRYPT.B. 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 the following Trend Micro Support pages for more information:

Step 7

Restore encrypted files from backup.


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