Analysis by: Raighen Sanchez
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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: 3,020,816 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 04 Dec 2023

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 terminates itself if it finds the following processes in the affected system's memory:

  • ntice.sys
  • iceext.sys
  • Syser.sys
  • HanOlly.sys
  • extrem.sys
  • FRDTSC.SYS
  • fengyue.sys
  • Kernel Detective
  • CisUtMonitor
  • FileMonitor.sys
  • REGMON
  • regsys
  • sysregm
  • PROCMON
  • Revoflt
  • Filem

Other System Modifications

This Ransomware sets the system's desktop wallpaper to the following image:

  • %Program Data%\CBhwKBgQD.bmp
  • %All Users Profile%\CBhwKBgQD.bmp

It uses Windows Management Instrumentation (WMI) to delete volume shadow copies:

  • SELECT * Win32_ShadowCopies

Other Details

This Ransomware does the following:

  • It terminates itself if found the following window name in the affected system:
    • OLLYDBG
    • GBDYLLO
    • pediy06
    • RegmonClass
    • Registry Monitor - Sysinternals: www.sysinternals.com
    • 18467-41
    • FilemonClass
    • File Monitor - Sysinternals: www.sysinternals.com
    • PROCMON_WINDOW_CLASS
    • Process Monitor - Sysinternals: www.sysinternals.com
  • It attempts to terminate running processes using the Restart Session Manager to encrypt the associated file as such will result to the following registry modification:
    • RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
      Owner = {hex values}

    • RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
      SessionHash = {hex values}

    • RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
      Sequence = 0x01

    • RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
      RegFiles{numbers} = {encrypted path andfile}

    • RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
      RegFilesHash = {hex values}
  • It reads the following registry keys to check for the BIOS version of the affected system:
    • HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\SystemBiosVersion
    • HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\VideoBiosVersion

Ransomware Routine

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

  • autorun.inf
  • boot.ini
  • bootfont.bin
  • bootsect.bak
  • d3d9caps.dat
  • desktop.ini
  • GDIPFONTCACHEV1.DAT
  • iconcache.db
  • ntldr
  • ntuser.dat
  • ntuser.dat.log
  • ntuser.ini
  • thumbs.db

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

  • $recycle.bin
  • $windows.~bt
  • $windows.~ws
  • all users
  • boot
  • config.msi
  • default
  • intel
  • microsoft
  • msocache
  • perflogs
  • program files
  • program files (x86)
  • programdata
  • public
  • system volume information
  • tor browser
  • windows
  • windows.old

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

  • {original filename}.{original extension}.CBhwKBgQD

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

  • {encrypted directory}\CBhwKBgQD.README.txt

It avoids encrypting files with the following file extensions:

  • 386
  • adv
  • ani
  • bat
  • bin
  • cab
  • cmd
  • com
  • cpl
  • cur
  • deskthemepack
  • diagcab
  • diagcfg
  • diagpkg
  • dll
  • drv
  • exe
  • hlp
  • hta
  • icl
  • icns
  • ico
  • ics
  • idx
  • key
  • ldf
  • lnk
  • lock
  • mod
  • mpa
  • msc
  • msi
  • msp
  • msstyles
  • msu
  • nls
  • nomedia
  • ocx
  • pdb
  • prf
  • ps1
  • rom
  • rtp
  • scr
  • search-ms
  • shs
  • spl
  • sys
  • theme
  • themepack
  • wpx

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 18.860.03
FIRST VSAPI PATTERN DATE: 05 Dec 2023
VSAPI OPR PATTERN File: 18.861.00
VSAPI OPR PATTERN Date: 06 Dec 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:

    •  Troj.Win32.TRX.XXPE50FFF075

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.

  • In RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
    • SessionHash = {hex values}
  • In RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
    • Sequence = 0x01
  • In RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
    • RegFiles{numbers} = {encrypted path and file}
  • In RegKey: HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session{numbers}
    • RegFilesHash = {hex values}

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}\CBhwKBgQD.README.txt
  • %Program Data%\CBhwKBgQD.bmp
  • %All Users Profile%\CBhwKBgQD.bmp

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.KASSEIKA.YPDLDT. 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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