How do you block Ctrl+Alt+Del, Alt+Tab and the windows logo button? Im making a small program called desktopShield that blocks access to the desktop and only allow access to whatever form is tied to 'Esc'.
Framework 2.0
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How do you block Ctrl+Alt+Del, Alt+Tab and the windows logo button? Im making a small program called desktopShield that blocks access to the desktop and only allow access to whatever form is tied to 'Esc'.
Framework 2.0
That is only possible using either,
1. Windows GINA.
2. Keyboard driver.
Both of them can not be programmed in .NET langs, only C/C++ can do that.
I found some code in the link below that blocks Alt+Tab. I've tried to put in the Ctrl+Alt+Del combination but it doesn't seem to work. And it doesn't have a const for the windows logo key.
http://www.codeguru.com/vb/gen/vb_sy...cle.php/c4831/
Here is an update I made from that example.
This really doesnt block the combo, but I have been able to modify this so you can change the ctl alt delete combo. Yes it exists in VB.NET.
Your on your own, if you need to block the combo.
Code:Imports System.Drawing
Imports System.Threading
Imports System.Reflection
Imports System.Runtime.InteropServices
Imports Microsoft.Win32
Friend Class Form1
Inherits System.Windows.Forms.Form
' Windows Form Designer generated code
Public Structure KBDLLHOOKSTRUCT
Public vkCode As Integer
Public scanCode As Integer
Public flags As Integer
Public time As Integer
Public dwExtraInfo As Integer
End Structure
Public Delegate Function KeyboardHookDelegate(ByVal Code As Integer, ByVal wParam As Integer, ByRef lParam As KBDLLHOOKSTRUCT) As Integer
<MarshalAs(UnmanagedType.FunctionPtr)> Private callback As KeyboardHookDelegate
Public KeyboardHandle As Integer
Const HC_ACTION As Integer = 0
Const WH_KEYBOARD_LL As Integer = 13&
Const SPI_SCREENSAVERRUNNING = 97
Const VK_ESCAPE As Integer = &H1B
Const VK_SHIFT As Integer = &H10
Const VK_CONTROL As Integer = &H11
Const VK_MENU As Integer = &H12
Const VK_DELETE As Integer = &H2E
Const VK_TAB As Integer = &H9
Const VK_LWIN As Integer = &H5B
Const VK_RWIN As Integer = &H5C
Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Integer) As Integer
Private Declare Function SystemParametersInfoByVal Lib "user32" Alias "SystemParametersInfoA" (ByVal uAction As Integer, ByVal uParam As Integer, ByVal lpvParam As Object, ByVal fuWinIni As Integer) As Integer
Public Declare Function SetWindowsHookEx Lib "user32" Alias "SetWindowsHookExA" (ByVal idHook As Integer, ByVal lpfn As KeyboardHookDelegate, ByVal hmod As Integer, ByVal dwThreadId As Integer) As Integer
Private Declare Function CallNextHookEx Lib "user32" (ByVal hHook As Integer, ByVal nCode As Integer, ByVal wParam As Integer, ByVal lParam As KBDLLHOOKSTRUCT) As Integer
Public Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hHook As Integer) As Integer
Dim clt() As Process = Process.GetProcessesByName("taskmgr")
Dim t As New Thread(AddressOf KillTask)
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
On Error Resume Next
If RadioButton1.Checked = True Then
Call SystemParametersInfoByVal(SPI_SCREENSAVERRUNNING, 1, "1", 0)
Else
HookKeyboard()
End If
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
On Error Resume Next
If RadioButton1.Checked = True Then
Call SystemParametersInfoByVal(SPI_SCREENSAVERRUNNING, 0, "1", 0)
Else
t.Abort()
UnhookKeyboard()
End If
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
On Error Resume Next
Dim regKey As RegistryKey
Dim regVal As String = ""
Registry.CurrentUser.CreateSubKey("Software\Microsoft\Windows\CurrentVersion\Policies\System")
regKey = Registry.CurrentUser.OpenSubKey("Software\Microsoft\Windows\CurrentVersion\Policies\System", True)
regKey.SetValue("DisableTaskMgr", 1)
regKey.Close()
regKey = Registry.CurrentUser.OpenSubKey("Control Panel\Desktop", True)
regVal = regKey.GetValue("ScreenSaveActive")
If regVal = "1" Then
regKey.SetValue("ScreenSaveActive", "0")
End If
regKey.Close()
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
On Error Resume Next
Dim regKey As RegistryKey
Dim regVal As String
Registry.CurrentUser.CreateSubKey("Software\Microsoft\Windows\CurrentVersion\Policies\System")
regKey = Registry.CurrentUser.OpenSubKey("Software\Microsoft\Windows\CurrentVersion\Policies\System", True)
regKey.SetValue("DisableTaskMgr", 0)
regKey.Close()
regKey = Registry.CurrentUser.OpenSubKey("Control Panel\Desktop", True)
regVal = regKey.GetValue("ScreenSaveActive")
If regVal = "0" Then
regKey.SetValue("ScreenSaveActive", "1")
End If
regKey.Close()
End Sub
Private Sub Form1_Closed(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Closed
On Error Resume Next
If RadioButton1.Checked = True Then
Call SystemParametersInfoByVal(SPI_SCREENSAVERRUNNING, 0, "1", 0)
Else
t.Abort()
UnhookKeyboard()
End If
End Sub
Public Sub KillTask()
On Error Resume Next
Do
Dim clt() As Process = Process.GetProcessesByName("taskmgr")
For Each p As Process In clt
p.Kill()
Next
System.Threading.Thread.Sleep(1)
Loop
End Sub
Public Function IsHooked(ByRef Hookstruct As KBDLLHOOKSTRUCT) As Boolean
On Error Resume Next
'Capture combos
If (Hookstruct.vkCode = VK_DELETE) And CBool(GetAsyncKeyState(VK_MENU) And &H8000) And CBool(GetAsyncKeyState(VK_CONTROL) And &H8000) Then
t.Start()
Return True
End If
If (Hookstruct.vkCode = VK_ESCAPE) And CBool(GetAsyncKeyState(VK_CONTROL) And &H8000) And CBool(GetAsyncKeyState(VK_SHIFT) And &H8000) Then
t.Start()
Return True
End If
'Capture your Alt + Tab combo here on your own, and return true
'Capture all your winlogo combos, and return true for each if/end if.
Return False
End Function
Public Sub HookKeyboard()
callback = New KeyboardHookDelegate(AddressOf KeyboardCallback)
KeyboardHandle = SetWindowsHookEx(WH_KEYBOARD_LL, callback, Marshal.GetHINSTANCE([Assembly].GetExecutingAssembly.GetModules()(0)).ToInt32, 0)
End Sub
Public Sub UnhookKeyboard()
If (Hooked()) Then
Call UnhookWindowsHookEx(KeyboardHandle)
End If
End Sub
Private Function Hooked()
Hooked = KeyboardHandle <> 0
End Function
Public Function KeyboardCallback(ByVal Code As Integer, ByVal wParam As Integer, ByRef lParam As KBDLLHOOKSTRUCT) As Integer
If (Code = HC_ACTION) Then
If (IsHooked(lParam)) Then
Return 1
End If
End If
Return CallNextHookEx(KeyboardHandle, Code, wParam, lParam)
End Function
Krishnaa, You can use Windows GINA with .NET. You can even use it with VB6, the only problem with it, is that some anti virus programs will think a Trojan is messing with it when you try to use it.
SystemParametersInfo is the way to go..
You could always load Calc.exe as the shell interface. Talk about a desktop shield!
I decided to block all keys except for the ones I specify. It works really well.