Ransom.BAT.CAI.THJBBAIA

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 encrypts files found in specific folders. 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 drops the following files:

• %Application Data%\wallpaper.jpg → used as wallpaper

(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:

• cmd /c ""{Malware Directory}\{Malware File Name}.bat" h" → if executed without “h” argument
• RunDll32.exe USER32.DLL,UpdatePerUserSystemParameters → updates wallpaper

Other System Modifications

This Ransomware changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %Application Data%\wallpaper.jpg

Other Details

This Ransomware does the following:

• It does not encrypt files. Instead, it encodes files to Base64.

It deletes itself after execution.

Ransomware Routine

This Ransomware encrypts files found in the following folders:

• {Malware Directory}

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

• .cxkdata.cxk_nmsl

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

• {Malware Directory}\CXK-NMSL-README.txt.exe
• {All directories in %SystemDrive%}\CXK-NMSL-README.txt.exe