Ransom.MSIL.OVAR.A

January 18, 2024
 Analysis by: John Rainier Navato
 ALIASES:

Gen:Variant.Zusy.496229 (BITDEFENDER)

 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, 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 adds certain registry entries to disable the Task Manager. This action prevents users from terminating the malware process, which can usually be done via the Task Manager.

It encrypts files found in specific folders. It drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

1,388,032 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Dec 2023

Payload:

Collects system information, Drops files, Disables programs, Encrypts files, Modifies system registry

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:

  • %AppDataLocal%\Var0Exploit\{Malware File Name}.{Malware File Extension}_Url_{Random}\1.0.0.0\{Random}.tmp → deleted afterwards
  • %AppDataLocal%\Var0Exploit\{Malware File Name}.{Malware File Extension}_Url_{Random}\1.0.0.0\{Random}.newcfg → renamed to user.config

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{Random} = {Malware File Path}\{Malware File Name}.{Malware File Extension}

Other System Modifications

This Ransomware adds the following registry entries to disable the Task Manager:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 1

Information Theft

This Ransomware gathers the following data:

  • Computer name
  • Processor ID
  • Motherboard Serial Number
  • System Drive Serial Number

Other Details

This Ransomware does the following:

  • It disables user input
  • It hides the Windows taskbar
  • It enters debug mode and sets itself as a critical Windows process.
  • It displays the following window in full screen:

Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • %Desktop%

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It avoids encrypting files with the following strings in their file path:

  • System Volume Information

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

  • .Var0Group

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

  • %Desktop%\message.html
  • {Available Drive Letter}:\message.html

It avoids encrypting files with the following file extensions:

  • .Var0Group

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

19.102.04

FIRST VSAPI PATTERN DATE:

17 Jan 2024

VSAPI OPR PATTERN File:

19.103.00

VSAPI OPR PATTERN Date:

18 Jan 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.XXPE50FFF076

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableTaskMgr = 1
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {Random} = {Malware File Path}\{Malware File Name}.{Malware File Extension}

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.
  • %AppDataLocal%\Var0Exploit\{Malware File Name}.{Malware File Extension}_Url_{Random}\1.0.0.0\{Random}.tmp
  • %AppDataLocal%\Var0Exploit\{Malware File Name}.{Malware File Extension}_Url_{Random}\1.0.0.0\user.config
  • %Desktop%\message.html
  • {Available Drive Letter}:\message.html

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.MSIL.OVAR.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.

Step 8

Restore encrypted files from backup.


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