Analysis by: Paul Steven Nadera
 ALIASES:

W32/Filecoder.OFO!tr.ransom (Fortinet)

 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, 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 avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

Tipo de compactação: 76,800 bytes
Tipo de arquivo: EXE
Residente na memória: Yes
Data de recebimento das amostras iniciais: 05 Mar 2021
Carga útil: Collects system information, 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:

  • %AppDataLocal%\{malware filename}.exe

(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:

  • %Public%\Libraries\{Generated ID} - contains unique identifier of the machine

(Note: %Public% is the folder that serves as a repository of files or folders common to all users, which is usually C:\Users\Public in Windows Vista, 7, and 8.)

It adds the following processes:

  • %System%\cmd.exe /c vssadmin.exe Delete Shadows /All /Quiet
  • reg delete HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Default /va /f
  • reg delete HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Servers /f
  • reg add HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Servers
  • cd %userprofile%\documents\
  • attrib Default.rdp -s -h
  • del Default.rdp
  • for /F tokens=* %1 in ('wevtutil.exe el') DO wevtutil.exe cl %1;

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 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\RunOnce
LicChk = %AppDataLocal%\{malware filename}.exe

Information Theft

This Ransomware gathers the following data:

  • Volume Info
  • MS Dos Device names
  • VolumePathNames

Other Details

This Ransomware does the following:

  • Encrypts the following drive types:
    • removable
    • fixed
    • network

It accepts the following parameters:

  • /f - Installs its dropped copy as autorun and deletes original file. Would not encrypt until restart.
  • /d

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file path:

  • ..
  • Mozilla
  • Intel
  • Temp
  • HOW_TO_RECOVERY_FILES.txt
  • $RECYCLE.BIN
  • .vscode
  • AVG
  • Avast
  • Avira
  • COMODO
  • Chrome
  • Common Files
  • Common7
  • Dr.Web
  • ESET
  • Firefox
  • InstallShield Installation Information
  • Internet Explorer
  • Kaspersky Lab
  • McAfee
  • Microsoft
  • Microsoft Help
  • Microsoft SDKs
  • Microsoft Shared
  • Microsoft VS Code
  • Microsoft Visual Studio
  • Microsoft.NET
  • Movie Maker
  • Mozilla Firefox
  • Reference Assemblies
  • NVIDIA Corporation
  • Opera
  • Outlook Express
  • Package Cache
  • Packages
  • ProgramData
  • Spytech software
  • Symantec
  • Symantec_Client_Security
  • System Volume Information
  • Windows
  • Windows App Certification Kit
  • Windows Defender
  • Windows Kits
  • Windows Mail
  • Windows Media Player
  • Windows Multimedia Platform
  • Windows NT
  • Windows Phone Kits
  • Windows Phone Silverlight Kits
  • Windows Photo Viewer
  • Windows Portable Devices
  • Windows Sidebar
  • Windows Security
  • WindowsPowerShell
  • WindowsApps
  • Wsus
  • YandexBrowser
  • sysconfig

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

  • .IQ07n

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

  • {encrypted directory}\HOW_TO_RECOVERY_FILES.txt

It avoids encrypting files with the following file extensions:

  • .msp
  • .rom
  • .rtp
  • .shs
  • .mod
  • .cur
  • .msc
  • .nomedia
  • .deskthemepack
  • .diagcab
  • .diagcfg
  • .msstyles
  • .scr
  • .hta
  • .idx
  • .ics
  • .lock
  • .diagpkg
  • .icns
  • .msi
  • .themepack
  • .bin
  • .theme
  • .bat
  • .cab
  • .nls
  • .spl
  • .icl
  • .sys
  • .drv
  • .lnk
  • .cmd
  • .adv
  • .cpl
  • .ico
  • .com
  • .exe
  • .ocx
  • .dll
  • .hlp
  • .mpa
  • .prf
  • .wpx
  • .ani
  • .msu
  • .ps1
  • .386
  • .IQ07n

  SOLUTION

Mecanismo de varredura mínima: 9.800
Primeiro arquivo padrão VSAPI: 16.576.05
Data do lançamento do primeiro padrão VSAPI: 05 Mar 2021
VSAPI OPR Pattern Version: 16.577.00
VSAPI OPR Pattern veröffentlicht am: 06 Mar 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.XXPE50FFF042

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.HELPYOU.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

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\RunOnce
    • LicChk = %AppDataLocal%\{malware filename}.exe

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%\{malware filename}.exe
  • %Public%\Libraries\{Generated ID} - contains unique identifier of the machine
  • {encrypted directory}\HOW_TO_RECOVERY_FILES.txt

Step 7

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.HELPYOU.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 8

Restore encrypted files from backup.


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