Analysis by: Nathaniel Gregory Ragasa
ALIASES:

Win64:Malware-gen(AVAST)

 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: 33,280 bytes
File Type: EXE
Memory Resident: No
Payload: 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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Local\azov
  • Local\Kasimir_C

Other System Modifications

This Ransomware modifies the following file(s):

  • %ProgramData%\rdpclient.exe → injects malicious codes.

(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.)

It adds the following registry entries:

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

Other Details

This Ransomware adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run\
Bandera

It does the following:

  • Checks if msiexec.exe or perfmon.exe is present in the machine:
    • if msiexec.exe or perfmon.exe is present checks if rdpclient.exe is present in the machine:
      • if rdpclient.exe is present, modifies rdpclient.exe(injects malicious codes).
  • Encrypts Fixed, Removable and Network Shares.
  • Encrypts if date and time is:
    • October 27, 2022 - 10:14:30 AM
  • Uses Intermittent Encryption - encrypts 666 bytes then skips 666 bytes

Ransomware Routine

This Ransomware 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 Directory}\RESTORE_FILES.txt

It avoids encrypting files with the following file extensions:

  • .dll
  • .exe
  • .ini
  • .azov

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 17.908.04
FIRST VSAPI PATTERN DATE: 29 Oct 2022
VSAPI OPR PATTERN File: 17.909.00
VSAPI OPR PATTERN Date: 30 Oct 2022

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.XXPE50FFF062

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

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 Directory}\RESTORE_FILES.txt

Step 6

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 7

Delete this registry key

[ 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

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win64.AZVO.THJCABB. 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 9

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.  

  • %ProgramData%\rdpclient.exe

Step 10

Restore encrypted files from backup.


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