Analysis by: Mohammed Malubay
ALIASES:

Ransom:Win32/DarkSide.DA(MICROSOFT); a variant of Win32/Filecoder.DarkSide.B trojan(NOD32);

 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: 57,856 bytes
File Type: EXE
Initial Samples Received Date: 24 May 2021

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:

  • {Malware Filepath}\{Malware Filename}.exe -work worker0 job0-{PID of running malicious process}
  • {Malware Filepath}\{Malware Filename}.exe -work worker1 job1-{PID of running malicious process}

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\vmvss
DeleteFlag = 1

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\VSS
DeleteFlag = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.{Random Characters}
(Default) = {Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
{Random Characters}\DefaultIcon
(Default) = %All Users Profile%\{Random Characters}.ico

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\vmvss
Start = 4

(Note: The default value data of the said registry entry is 3.)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\VSS
Start = 4

(Note: The default value data of the said registry entry is 3.)

Dropping Routine

This Ransomware drops the following files:

  • %All Users Profile%\{Random Characters}.ico

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

Other Details

This Ransomware adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.{Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
{Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
{Random Characters}\DefaultIcon

It adds and runs the following services:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
Type = 16

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
ErrorControl = 0

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
ImagePath = "{Malware Filepath}\{Malware Filename}.exe"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
DisplayName = .{Random Characters}

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
ObjectName = LocalSystem

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
DeleteFlag = 1

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\.{Random Characters}
Start = 4

Ransomware Routine

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

  • .{Random Characters}

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

  • {Encrypted Directory}\README.{Random Characters}.TXT

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.668.04
FIRST VSAPI PATTERN DATE: 20 Apr 2021
VSAPI OPR PATTERN File: 16.669.00
VSAPI OPR PATTERN Date: 21 Apr 2021

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.XXPE50FFF044

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_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • Type = 16
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • Start = 3
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • ErrorControl = 0
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • ImagePath = "{Malware Filepath}\{Malware Filename}.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • DisplayName = .{Random Characters}
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • ObjectName = LocalSystem
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • DeleteFlag = 1
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
    • Start = 4
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\vmvss
    • DeleteFlag = 1
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\VSS
    • DeleteFlag = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.{Random Characters}
    • (Default) = {Random Characters}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\{Random Characters}\DefaultIcon
    • (Default) = %All Users Profile%\{Random Characters}.ico

Step 6

Delete this registry key

[ 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_LOCAL_MACHINE\SYSTEM\ControlSet001\services\.{Random Characters}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.{Random Characters}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\{Random Characters}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\{Random Characters}\DefaultIcon

Step 7

Restore this modified 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_LOCAL_MACHINE\SYSTEM\ControlSet001\services\VSS
    • Start = 4
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\vmvss
    • Start = 4

Step 8

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.
  • %All Users Profile%\{Random Characters}.ico
  • {Encrypted Directory}\README.{Random Characters}.TXT

Step 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.DARSKIDE.YXBDT. 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 10

Restore encrypted files from backup.


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