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Ransom.Win32.RYUK.HUI

January 06, 2020
 Analysis by: Arianne Grace Dela Cruz
 ALIASES:

Gen:Variant.Ulise.93501 (BITDEFENDER); Trojan.Win32.Crypt (IKARUS)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 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.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

687,344 bytes

File Type:

EXE

Initial Samples Received Date:

25 Dec 2019

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:

  • {Malware Directory}\{random file name}.exe

It adds the following processes:

  • "{Malware Directory}\{Random Filename}.exe 8 LAN"
  • net stop "audioendpointbuilder" /y
  • net stop "samss" /y
  • net stop "ui0detect" /y
  • net1 stop "audioendpointbuilder" /y
  • net1 stop "samss" /y
  • net1 stop "ui0detect" /y
  • icacls "A:\*" /grant Everyone:F /T /C /Q
  • icacls "C:\*" /grant Everyone:F /T /C /Q
  • icacls "D:\*" /grant Everyone:F /T /C /Q
  • icacls "E:\*" /grant Everyone:F /T /C /Q
  • vssadmin.exe Delete Shadows /all /quiet

Ransomware Routine

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

  • .RYK

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

  • {folder of encrypted files}\RyukReadMe.html

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.580.03

FIRST VSAPI PATTERN DATE:

25 Dec 2019

VSAPI OPR PATTERN File:

15.581.00

VSAPI OPR PATTERN Date:

26 Dec 2019

Step 1

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 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 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.
  • {folder of encrypted files}\RyukReadMe.html

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.RYUK.HUI. 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 6

Restore encrypted files from backup.


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