Analysis by: Kyle Philippe Yu

ALIASES:

DeepScan:Generic.Ransom.AmnesiaE.FC97BF15 (BITDEFENDER)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: 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 drops files as ransom note.

  TECHNICAL DETAILS

File Size: 826,880 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 30 Mar 2023
Payload: Terminates processes, Modifies system registry, 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 adds the following processes:

  • cmd /c wmic shadowcopy delete/nointeractive
  • cmd /c vssadmin.exe Delete Shadows /All /Quiet
  • cmd /c bcdedit /set {default} recoveryenabled No
  • cmd /c bcdedit /set {default} bootstatuspolicy ignoreallfailures
  • cmd /c powershell -command "Get-EventLog -LogName * | ForEach {Clear-EventLog $_.Log}"
  • powershell -Command "$a = [System.IO.File]::ReadAllText(\"D:\GET_YOUR_FILES_BACK.txt\");Add-Type -AssemblyName System.Drawing;$filename = \"$env:temp\$(Get-Random).png\";$bmp = new-object System.Drawing.Bitmap 1920,1080;$font = new-object System.Drawing.Font Consolas,10;$brushBg = [System.Drawing.Brushes]::Black;$brushFg = [System.Drawing.Brushes]::White;$format = [System.Drawing.StringFormat]::GenericDefault;$format.Alignment = [System.Drawing.StringAlignment]::Center;$format.LineAlignment = [System.Drawing.StringAlignment]::Center;$graphics = [System.Drawing.Graphics]::FromImage($bmp);$graphics.FillRectangle($brushBg,0,0,$bmp.Width,$bmp.Height);$graphics.DrawString($a,$font,$brushFg,[System.Drawing.RectangleF]::FromLTRB(0, 0, 1920, 1080),$format);$graphics.Dispose();$bmp.Save($filename);reg add \"HKEY_CURRENT_USER\Control Panel\Desktop\" /v Wallpaper /t REG_SZ /d $filename /f;Start-Sleep 1;rundll32.exe user32.dll, UpdatePerUserSystemParameters, 0, $false;"
  • %System%\reg.exe add "HKEY_CURRENT_USER\Control Panel\Desktop" /v Wallpaper /t REG_SZ /d %User Temp%\{10 Random Digits}.png /f
  • %System%\rundll32.exe user32.dll UpdatePerUserSystemParameters 0 False

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

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Zheic0WaWie6zeiy

Other System Modifications

This Ransomware modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %User Temp%\{10 Random Digits}.png

Process Termination

This Ransomware terminates the following processes if found running in the affected system's memory:

  • encsvc
  • thebat
  • mydesktopqos
  • xfssvccon
  • firefox
  • infopath
  • winword
  • steam
  • synctime
  • notepad
  • ocomm
  • onenote
  • mspub
  • thunderbird
  • agntsvc
  • sql
  • excel
  • powerpnt
  • outlook
  • wordpad
  • dbeng50
  • isqlplussvc
  • sqbcoreservice
  • oracle
  • ocautoupds
  • dbsnmp
  • msaccess
  • tbirdconfig
  • ocssd
  • mydesktopservice
  • visio

Other Details

This Ransomware does the following:

  • Displays encryption progress in console
  • Encrypts files found in the following drives: Fixed Drives, Removable Drives, Network Share Drives
  • If the file is currently being used by another process, the ransomware kills the process and proceeds with encryption

It accepts the following parameters:

  • -p, --path [Path to Encrypt]
  • -b, --brutesmb [Bruteforce SMB for logical drives]
  • --nomutex [Disable mutex / ignore other instances]
  • -l, --disabledrives [Disable logical drives enumeration]
  • -n, --enablesmb [Enable SMB enumeration]
  • --hide [hide console window]
  • -t, --threads [No of Threads] [Max threads for encryption (default:200)]
  • -h, --help [Print usage]

Ransomware Routine

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

  • autorun.inf
  • boot.ini
  • bootfont.bin
  • bootsect.bak
  • config.msi
  • desktop.ini
  • iconcache.db
  • ntldr
  • ntuser.dat
  • ntuser.dat.log
  • ntuser.ini
  • thumbs.db
  • Thumbs.db

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

  • All Users
  • AppData
  • boot
  • bootmgr
  • Games
  • Intel
  • Program Files
  • ProgramData
  • Public
  • Sophos
  • System Volume Information
  • Windows
  • Windows.old
  • WinNT
  • Microsoft

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

  • .avos2

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

  • %Desktop%\GET_YOUR_FILES_BACK.txt
  • {Encrypted Directory}\GET_YOUR_FILES_BACK.txt
  • %User Temp%\{10 Random Digits}.png

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 18.354.02
FIRST VSAPI PATTERN DATE: 31 Mar 2023
VSAPI OPR PATTERN File: 18.355.00
VSAPI OPR PATTERN Date: 01 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:

     
    • Ransom.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

Identify and terminate files detected as Ransom.Win32.AVOSLOCKER.I

[ 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 6

Search and delete these files

[ 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.
  • %User Temp%\{10 Random Digits}.png
  • %Desktop%\GET_YOUR_FILES_BACK.txt
  • {Encrypted Directory}\GET_YOUR_FILES_BACK.txt

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.AVOSLOCKER.I. 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 8

Restore encrypted files from backup.

Step 9

Reset your Desktop properties

[ Learn More ]


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