Ransom.Win32.AVOSLOCKER.I

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.

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