Analysis by: Mohammed Malubay
ALIASES:

HEUR:Trojan-Ransom.MSIL.Encoder.gen(KASPERSKY); Ransom:Win32/Higuniel.A(MICROSOFT); a variant of MSIL/Filecoder.Jigsaw.V 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

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.

It deletes itself after execution.

It drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size: 28,160 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 16 Dec 2019
Payload: Encrypts files, Deletes self after executing 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 files:

  • %Application Data%\Temp (x86)\SINFO.txt - contains Machine Name, Username, randomized password (used for encrypting files) and VolumeSerial
  • %Application Data%\Temp (x86)\Encrypted-Files.txt - list of all encrypted files

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

It adds the following processes:

  • notepad.exe %Desktop%\How_To_Restore_Your_Files.txt
  • explorer.exe %Desktop%\info.hta
  • mshta.exe %Desktop%\info.hta
  • cmd.exe /C timeout 2 && Del /Q /F {full file path of malware file}

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It creates the following folders:

  • %Application Data%\Temp (x86)

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

Autostart Technique

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

SOFTWARE\Microsoft\Windows\
CurrentVersion\Run
info.hta = "%Application Data%\Temp (x86)\info.hta"

Other Details

This Ransomware does the following:

  • It encrypts the following drives:
    • C:\
    • D:\
    • E:\
    • F:\
    • G:\
    • H:\
    • I:\
    • J:\
    • K:\

It deletes itself after execution.

Ransomware Routine

This Ransomware avoids encrypting files found in the following folders:

  • %Application Data%\Temp (x86)
  • C:\Program Files (x86)\Internet Explorer
  • C:\Program Files\Internet Explorer
  • C:\Windows
  • D:\Windows

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

It appends the following extension to the file name of the encrypted files:

  • .{BLOCKED}rypt[{BLOCKED}acker@protonmail.com]-[ID-{VolumeSerial}].Encrypted

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

  • %Application Data%\Temp (x86)\info.hta

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

  • {Encrypted Directory}\How_To_Restore_Your_Files.txt
  • %Desktop%\How_To_Restore_Your_Files.txt

It avoids encrypting files with the following file extensions:

  • .Encrypted

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.562.03
FIRST VSAPI PATTERN DATE: 16 Dec 2019
VSAPI OPR PATTERN File: 15.563.00
VSAPI OPR PATTERN Date: 17 Dec 2019

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.XXPE50FFF033

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
    • info.hta = "%Application Data%\Temp (x86)\info.hta"

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.
  • %Application Data%\Temp (x86)\SINFO.txt
  • %Application Data%\Temp (x86)\Encrypted-Files.txt
  • %Application Data%\Temp (x86)\info.hta
  • %Desktop%\info.hta
  • %Desktop%\How_To_Restore_Your_Files.txt
  • {Encrypted Directory}\How_To_Restore_Your_Files.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.
  • %Application Data%\Temp (x86)

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.MSIL.SPARTCRYPT.A. 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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