Ransom.Win64.AZVO.A

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.

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 infected with azvo ransomware 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 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 checks if msiexec.exe or perfmon.exe is present in the machine's %System% folder:
  • If msiexec.exe or perfmon.exe is present, it checks if rdpclient.exe is present in the machine's %ProgramData% folder:
    • If rdpclient.exe is not present, it copies msiexec.exe or perfmon.exe as rdpclient.exe in %ProgramData% and injects malicious codes to it.
• It only encrypts if date and time is on or after:
  • Oct 27, 2022 10:14:29 AM
• It uses intermittent encryption - encrypts 666 bytes then skips 666 bytes
• It injects its code to executable files that meets the following conditions:
  • The file is not found in the list of avoided folders/paths
  • The file extension is .exe
  • The file size is less than 20MB
  • The file is a 64-bit executable file
  • The PE section containing the entry point has enough space for the shellcode to be injected

(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
• Program Data
• cache2\entries
• Low\Content.IE5
• User Data\Default\Cache
• Documents and Settings
• All Users

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

• .azov

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

• {Encrypted Path}\RESTORE_FILES.txt
  

It avoids encrypting files with the following file extensions:

• .dll
• .exe
• .ini
• .azov