Ransom.MSIL.TPRC.A

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 connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

It encrypts files with specific file extensions. 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 copies of itself into the affected system:

• %ProgramData%\00aaaa.exe → created only if the environment variable "00MYEXE" is present

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.)

It drops the following files:

• %User Temp%\wp.png → image used as system wallpaper after encryption
• %ProgramData%\00aaaa.ps1 → created only if the environment variable "00MYSCR" is present

(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).. %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.)

It adds the following processes:

• {Microsoft .NET Runtime Directory}\RegAsm.exe
• %System%\Wbem\wmic.exe shadowcopy delete

(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\Run
00aaaa = %System%\WindowsPowerShell\v1.0\powershell.exe -ep bypass %ProgramData%\00aaaa.ps1 → created only if the environment variable "00MYSCR" is present

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
00aaaa = %ProgramData%\00aaaa.exe → created only if the environment variable "00MYEXE" is present

Other System Modifications

This Ransomware sets the system's desktop wallpaper to the following image:

• %User Temp%\wp.png

(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).)

Download Routine

This Ransomware connects to the following URL(s) to download its component file(s):

• https://{BLOCKED}tdn.de/wallpaper?ip={Affected System's IP Address} → Downloads the image used as system wallpaper after encryption, however as of this writing the said site is inaccessible.

Other Details

This Ransomware connects to the following website to send and receive information:

• https://{BLOCKED}tdn.de/log?ip={Affected System's IP Address}&message=TC04/12 {Malware Status}

However, as of this writing, the said sites are inaccessible.

Ransomware Routine

This Ransomware encrypts files with the following extensions:

• .7z
• .avi
• .doc
• .docx
• .dwg
• .flv
• .gif
• .jpg
• .log
• .mkv
• .mov
• .mp3
• .mp4
• .ods
• .odt
• .pdf
• .png
• .ppt
• .pptx
• .psd
• .rar
• .txt
• .vob
• .wav
• .wma
• .wma
• .xls
• .xlsx
• .zip

It encrypts files found in the following folders:

• %User Profile%

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

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

• .tprc

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

• {Discovered Directory}\!RESTORE!.txt