Analysis by: Bren Matthew Ebriega
 ALIASES:

Ransom:Win32/SanwaiCrypt.PA!MTB (MICROSOFT)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Canal de infecção: Downloaded from the Internet

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 encrypts files with specific file extensions. It encrypts files found in specific folders. It drops files as ransom note.

  TECHNICAL DETAILS

Tipo de compactação: 504,320 bytes
Tipo de arquivo: EXE
Residente na memória: No
Data de recebimento das amostras iniciais: 06 Sep 2021
Carga útil: Displays message/message boxes, Encrypts 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:

  • %Desktop%\decryptor.exe

(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 adds the following processes:

  • %System%\cmd.exe /c IMPORTANT.html
  • The following processes run in a loop:
    • %System%\cmd.exe /c taskkill /f /im cmd.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im HTTPDebuggerUI.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im HTTPDebuggerSvc.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im Ida64.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im OllyDbg.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im Dbg64.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im Dbg32.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im HxD.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im regedit.exe >nul 2>&1
    • %System%\cmd.exe /c taskkill /f /im Taskmgr.exe >nul 2>&1
    • %System%\cmd.exe /c sc stop HTTPDebuggerPro >nul 2>&1
    • %System%\cmd.exe /c taskkill /FI "IMAGENAME eq cheatengine*" /IM * /F /T >nul 2>&1
    • %System%\cmd.exe /c taskkill /FI "IMAGENAME eq httpdebugger*" /IM * /F /T >nul 2>&1
    • %System%\cmd.exe /c taskkill /FI "IMAGENAME eq processhacker*" /IM * /F /T >nul 2>&1

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .txt
  • .exe
  • .pdf
  • .csv
  • .doc
  • .word
  • .cpp
  • .h
  • .mp3
  • .wav
  • .zip
  • .rar
  • .sql
  • .gif
  • .jpg
  • .png
  • .jpeg
  • .psd

It encrypts files found in the following folders:

  • %SystemRoot%\Users\

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

  • .sanwai
  • .sanwai2
  • .sanwai3
  • .sanwai4
  • .sanwai5
  • .sanwai6
  • .sanwai7
  • .sanwai8
  • .sanwai9
  • .sanwai10
  • .sanwai11
  • .sanwai12
  • .sanwai13
  • .sanwai14
  • .sanwai15
  • .sanwai16
  • .sanwai17
  • .sanwai18

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

  • %Desktop%\IMPORTANT.html

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

  • {Encrypted Folder}\IMPORTANT.txt

  SOLUTION

Mecanismo de varredura mínima: 9.800
Primeiro arquivo padrão VSAPI: 16.942.05
Data do lançamento do primeiro padrão VSAPI: 02 Sep 2021
VSAPI OPR Pattern Version: 16.943.00
VSAPI OPR Pattern veröffentlicht am: 03 Sep 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.XXPE50FFF049

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

Identify and terminate files detected as Ransom.Win32.SANWAI.A

[ 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 5

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.
  • {Encrypted Folder}\IMPORTANT.txt
  • %Desktop%\IMPORTANT.html
  • %Desktop%\decryptor.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.SANWAI.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 the following Trend Micro Support pages for more information:

Step 7

Restore encrypted files from backup.


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