Analysis by: Raymart Christian Yambot
ALIASES:

UDS:Trojan-Ransom.Win32.Encoder.yhh (KASPERSKY)

 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: 2,366,976 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 05 Jul 2024
Payload: Connects to URLs/IPs, 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:

  • %User Temp%\Wallpaper.png

(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:

  • powershell -Command "(New-Object System.Net.WebClient).DownloadFile('https://i.imgur.com/RfsCOES.png', '%User Temp%\Wallpaper.png')"
  • powershell -Command "Add-Type -TypeDefinition 'using System; using System.Runtime.InteropServices; public class Wallpaper { [DllImport(\"user32.dll\", CharSet = CharSet.Auto)] public static extern int SystemParametersInfo(int uAction, int uParam, string lpvParam, int fuWinIni); public static void Set(string path) { SystemParametersInfo(20, 0, path, 3); } }'; [Wallpaper]::Set('%User Temp%\Wallpaper.png')"

Other System Modifications

This Ransomware sets the system's desktop wallpaper to the following image:

  • %User Temp%\Wallpaper.png

Download Routine

This Ransomware accesses the following websites to download files:

  • https://{BLOCKED}r.com/RfsCOES.png

Ransomware Routine

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

  • bootmgr
  • bcd
  • desktop.ini
  • config.sys
  • autoexec.bat
  • decryption instructions.txt

It avoids encrypting files found in the following folders:

  • windows
  • system32
  • programdata
  • program files
  • program files (x86)
  • public
  • system volume information
  • \system volume information
  • efi
  • boot
  • public
  • perflogs
  • microsoft
  • intel
  • appdata
  • .dotnet
  • .gradle
  • .nuget
  • .vscode
  • msys64

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

  • {Encrypted Directory}\decryption instructions.txt

It avoids encrypting files with the following file extensions:

  • .sys
  • .exe
  • .dll
  • .com
  • .scr
  • .bat
  • .vbs
  • .ps1
  • .lnk
  • .inf
  • .reg
  • .msi
  • .ini

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 19.448.04
FIRST VSAPI PATTERN DATE: 05 Jul 2024
VSAPI OPR PATTERN File: 19.449.00
VSAPI OPR PATTERN Date: 06 Jul 2024

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.XXPE50FFF085

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

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.
  • %User Temp%\Wallpaper.png

Step 5

Reset your Desktop properties

[ Learn More ]

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win64.PIRCEN.THHOEBD.go. 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:


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