Ransom.Win32.ENQTOX.A.go

 Analysis by: Ricardo III Valdez

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • 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:

2,418,688 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

01 Jan 2023

Payload:

Displays message/message boxes, Deletes registry key, Drops 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:

  • %Public%\.lock
  • %Public%\sd\del.bat
  • %Public%\Desktop\decrypt.key
  • %Public%\Desktop\Readme_on_Chrome.html ← Ransom Note
  • %User Profile%\Administrator\Desktop\Readme_on_Chrome.html ← Ransom Note
  • {Malware File Path}\files.txt

(Note: %Public% is the folder that serves as a repository of files or folders common to all users, which is usually C:\Users\Public in Windows Vista, 7, and 8.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • reg delete "HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Default" /va " /f"
  • reg delete "HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Servers" " /f"
  • reg delete HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\WordWheelQuery " /f"
  • reg delete HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\TypedPaths " /f"
  • reg delete HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU " /f"
  • wevtutil cl system ← Clears system logs
  • wevtutil cl security ← Clears security logs
  • vssadmin delete shadows " /all" /quiet ← Deletes shadow copies

Other System Modifications

This Ransomware deletes the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Terminal Server Client\Default
(Default) =

HKEY_CURRENT_USER\Software\Microsoft\
Terminal Server Client\Servers
(Default) =

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
WordWheelQuery
(Default) =

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
TypedPaths
(Default) =

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
RunMRU
(Default) =

Ransomware Routine

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

  • private.pem
  • public.pem
  • files.txt
  • golancer.key
  • decrypt.key
  • desktop.ini
  • Readme.html
  • Readme_on_Chrome.html

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

  • {Original Filename & File Extension}.[get_readme_on_desktop]

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

  • %Public%\Desktop\Readme_on_Chrome.html
  • %User Profile%\Administrator\Desktop\Readme_on_Chrome.html

It avoids encrypting files with the following file extensions:

  • .exe
  • .dll
  • .sys
  • .lnk
  • .msi
  • .hta
  • .cpl
  • .ini
  • .cab
  • .cur
  • .idx
  • .drv
  • .hlp
  • .icl
  • .icns
  • .ico
  • .ocx
  • .spl
  • .bat
  • .bin
  • .pak
  • .lock

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.190.04

FIRST VSAPI PATTERN DATE:

12 Jan 2023

VSAPI OPR PATTERN File:

18.191.00

VSAPI OPR PATTERN Date:

13 Jan 2023

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.XXPE50FFF064

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 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.  
  • %Public%\.lock
  • %Public%\sd\del.bat
  • %Public%\Desktop\decrypt.key
  • %Public%\Desktop\Readme_on_Chrome.html
  • %User Profile%\Administrator\Desktop\Readme_on_Chrome.html
  • {Malware File Path}\files.txt

Step 5

Enabling Volume Shadow Service

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Volume Shadow Service by typing the following command:
    net start vss

Step 6

Restore encrypted files from backup.

Step 7

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\
    • Default
  • In HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\
    • Servers
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\
    • WordWheelQuery
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\
    • TypedPaths
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\
    • RunMRU

Step 8

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.ENQTOX.A.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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