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Ransom.Win32.STOP.YCDC5

April 06, 2023
 Analysis by: Jeffrey Francis Bonaobra
 ALIASES:

Ransom.Stop.P5 (QUICKHEAL)

 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

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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:

766,976 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

31 Mar 2023

Payload:

Creates files, Connects to URLs/IPs, Drops files, Modifies files

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:

  • %AppDataLocal%\{GUID}\{Malware File Name}

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It drops the following files:

  • %AppDataLocal%\bowsakkdestx.txt → deleted afterwards
  • %System Root%\SystemID\PersonalID.txt

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

It adds the following processes:

  • {Malware File Path}\{Malware File Name}
  • icacls "%AppDataLocal%\{GUID}" /deny *S-1-1-0:(OI)(CI)(DE,DC)
  • {Malware File Path}\{Malware File Name} --Admin IsNotAutoStart IsNotTask

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It creates the following folders:

  • %AppDataLocal%\{GUID}
  • %System Root%\SystemID

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
SysHelper = "%AppDataLocal%\{GUID}\{Malware File Name}.exe" --AutoStart

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
SysHelper = 1

Other Details

This Ransomware connects to the following possibly malicious URL:

  • https://api.{BLOCKED}p.ua
  • http://{BLOCKED}y.top/dl/build2.exe
  • http://{BLOCKED}q.com/raud/get.php?pid={Hash}&first=true
  • http://{BLOCKED}q.com/files/1/build3.exe
  • https://api.{BLOCKED}p.ua/geo.json
  • http://{BLOCKED}q.com/raud/get.php?pid={Hash}

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

Ransomware Routine

This Ransomware renames encrypted files using the following names:

  • {Original Filename}.{Original Extension}.jyos

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

  • {Encrypted Directory}\_readme.txt

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.356.06

FIRST VSAPI PATTERN DATE:

01 Apr 2023

VSAPI OPR PATTERN File:

18.357.00

VSAPI OPR PATTERN Date:

02 Apr 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.XXPE50FFF067

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 value

[ 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 HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • SysHelper = "%AppDataLocal%\{GUID}\{Malware File Name}.exe" --AutoStart
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • SysHelper = 1

Step 6

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.
  • %AppDataLocal%\{GUID}\{Malware File Name}
  • %AppDataLocal%\bowsakkdestx.txt
  • %System Root%\SystemID\PersonalID.txt
  • {Encrypted Directory}\_readme.txt

Step 7

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %AppDataLocal%\{GUID}
  • %System Root%\SystemID

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.STOP.YCDC5. 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 9

Restore encrypted files from backup.


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