Analysis by: Bren Matthew Ebriega
ALIASES:

Ransom:Win32/Ryuk.B (MICROSOFT); HEUR:Trojan.Win32.Generic (KASPERSKY)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

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.

  TECHNICAL DETAILS

File Size: 261,784 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 08 Nov 2020
Payload: Deletes files, Displays graphics/image

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:

  • %System%\cmd.exe shutdown /r /t 10 /f → If registry entry is found
  • %System%\cmd.exe /c color 0A

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

Other System Modifications

This Ransomware deletes the following files:

  • Files with the filename RyukReadMe.html.

Other Details

This Ransomware does the following:

  • It displays the following window:
  • It attempts to decrypt files with .RYK extension in FIXED, REMOVABLE and REMOTE drives.
  • It renames .RYK extension files by removing the .RYK extension.
  • It deletes the following registry entry:
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      svchos = {Empty or Not Empty}

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.342.03
FIRST VSAPI PATTERN DATE: 09 Nov 2020
VSAPI OPR PATTERN File: 16.343.00
VSAPI OPR PATTERN Date: 10 Nov 2020

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.XXPE50FFF038

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

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.RYUK.FAILDEC. 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:


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