Ransom.MSIL.FREEZING.A

This ransomware is one of the few ransomware families that is loaded and executed under the legitimate PowerShell executable. It also is one of the few that uses restart session manager to terminate processes that have associated files it tries to encrypt.

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.

This malware arrives via the following means:

• Injected in Powershell.exe process by Trojan.PS1.FREEZING.A

Dropping Routine

This Ransomware drops the following files:

• %ProgramData%\.FreezedByMagic.LOG - contains the following information:
  • Malware Process ID
  • Processor Count
  • Drives to encrypt
  • Total number fo files encrypted
  • Duration of encryption (in seconds and minutes)

(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.)

Other Details

This Ransomware does the following:

• It encrypts files in available fixed and removable drives.
• It attempts to terminate running processes using the Restart Session Manager to encrypt the associated file as such will result to the following registry modifications:
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\RestartManager\Session{numbers}
  • RegFiles{numbers} = {Encrypted File and Path}
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\RestartManager\Session{numbers}
  • RegFilesHash = {Hex Values}
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\RestartManager\Session{numbers}
  • Sequence = 0x01
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\RestartManager\Session{numbers}
  • SessionHash = {Hex Values}
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\RestartManager\Session{numbers}
  • Owner = {Hex Values}

Ransomware Routine

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

• .exe
• .sys
• .dll
• .msi
• .iso
• .cab
• .ReadMe.txt
• .LOG

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

• Windows
• ProgramData
• ProgramFiles
• Boot

It renames encrypted files using the following names:

• {filename and extension}.Freezing - during encryption
• {filename and extension}.FreezedByWizard - after successful encryption

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

• {drive of encrypted files}\.FreezedByWizard.README.TXT

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