Analysis by: Carlos Villegas Madrid
 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 avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size: 179,200 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 Feb 2023
Payload: Encrypts files, Displays message/message boxes

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 processes:

  • if --safe-mode commandline parameter is used:
    • "%System%\bcdedit.exe" /set {default} safeboot network
    • "%System%\shutdown.exe" -r

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Autostart Technique

This Ransomware registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\nokonoko → if --safe-mode commandline parameter is used.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\nokonoko → if --safe-mode commandline parameter is used.

Other Details

This Ransomware does the following:

  • The following can be changed in the runtime configuration:
    • Directories to avoid
    • File extensions to avoid
    • Ransom note content
    • Ransom note filename
    • Appended extension of encrypted files
  • The following can be enabled/disabled in the runtime configuration:
    • Encryption of network shares
    • Delete shadow copies
    • Loading of hidden drives

It accepts the following parameters:

  • --config {Base64 encoded config} → runtime configuration of the sample.
  • --safe-mode → reboots and encrypts the user's machine in safe mode
  • --file {File Path} → encrypt selected files
  • --dir {Directory Path}→ encrypt selected directories and sub-directories

It does not proceed to its malicious routine if it detects that it is being debugged.

Ransomware Routine

This Ransomware avoids encrypting files found in the following folders:

  • windows
  • program files
  • program files (X86)
  • appdata
  • programdata
  • system volume information

It leaves text files that serve as ransom notes containing the following text:

  • {Encrypted Directory}\NOKONOKO-readme.txt

It avoids encrypting files with the following file extensions:

  • .exe
  • .dll
  • .ini
  • .lnk
  • .url

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 18.258.05
FIRST VSAPI PATTERN DATE: 15 Feb 2023
VSAPI OPR PATTERN File: 18.259.00
VSAPI OPR PATTERN Date: 16 Feb 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:

     
    • Mal.Win32.TRX.XXPE50FFF065

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 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\nokonoko
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\nokonoko

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.  
  • {Encrypted Directory}\NOKONOKO-readme.txt

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win64.NOKO.YPDBO. 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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