Analysis by: Carl Maverick Pascual
ALIASES:

Gen:Variant.Ursu.576438 (BitDefender); Win32:Trojan-gen (AVAST)

 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.

  TECHNICAL DETAILS

File Size: 755,200 bytes
File Type: EXE
Initial Samples Received Date: 03 Sep 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 Filaname}.exe 8 LAN"
  • net stop "audioendpointbuilder" /y
  • net stop "samss" /y
  • net1 stop "audioendpointbuilder" /y
  • net1 stop "samss" /y

Ransomware Routine

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

  • .RYK

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

  • RyukReadMe.html

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.342.08
FIRST VSAPI PATTERN DATE: 03 Sep 2019
VSAPI OPR PATTERN File: 15.343.00
VSAPI OPR PATTERN Date: 04 Sep 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

Identify and terminate files detected as Ransom.Win32.RYUK.HTW

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.RYUK.HTW. 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 5

Restore encrypted files from backup.


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