Ransom.Win64.AZVO.B

February 12, 2025
 Analysis by: Paolo Ronniel Labrador
 ALIASES:

Win32:Azov-A [Wpr] (AVAST)

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

  TECHNICAL DETAILS

File Size:

32,768 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

31 Oct 2022

Payload:

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%\rdpclient.exe ← copy of %System%\msiexec.exe or %System%\perfmon.exe with injected malicious code

(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:

  • Local\azov
  • Local\Kasimir_{letter of drive where files are being encrypted}

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Bandera = %ProgramData%\rdpclient.exe

Other Details

This Ransomware does the following:

  • It searches for files in Removable, Fixed or Network drives
    • Then it injects malicious code to files that meet the following conditions:
      • If the file is not found in avoided folders
      • If the file extension is .exe
      • If the file size is less than 20MB
      • If the file is a 64-bit executable
      • If the section containing the entry point has enough space for the malicious code
  • It checks if msiexec.exe or perfmon.exe is present in %System% folder
    • Then it checks if rdpclient.exe exists in %ProgramData%
      • Creates a file named rdpclient.exe, copies the content of msiexec.exe or perfmon.exe into rdpclient.exe, and injects malicious code into it.

(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.)

Ransomware Routine

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

  • RESTORE_FILES.txt

It avoids encrypting files found in the following folders:

  • Windows
  • ProgramData
  • Cache2\entries
  • Low\Content.IE5
  • User Data\Default\Cache
  • Documents and Settings
  • All Users

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

  • {Encrypted Path}\RESTORE_FILES.txt

It avoids encrypting files with the following file extensions:

  • .exe
  • .dll
  • .ini

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

19.894.04

FIRST VSAPI PATTERN DATE:

11 Feb 2025

VSAPI OPR PATTERN File:

19.895.00

VSAPI OPR PATTERN Date:

12 Feb 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.XXPE50FFF090

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
    • Bandera = %ProgramData%\rdpclient.exe

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%\rdpclient.exe
  • {Encrypted Path}\RESTORE_FILES.txt

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win64.AZVO.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 this Knowledge Base page for more information.

Step 8

Restore encrypted files from backup.


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