Dato che al primo messaggio ho parlato delle "librerie hook", metto qui di seguito un esempio di quello a cui facevo riferimento.
A quanto pare - comunque - la combinazione CTRL+ALT+CANC non viene bloccata neanche con questo metodo e infatti il programmatore che ha fatto il codice seguente ha previsto una procedura per chiudere il task manager.
VB.NET - Disabilitare o Intercettare i tasti speciali di Windows (Codice)
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Oggi vi voglio mettere a disposizione una funzione che ho trovato su internet, che serve per intercettare i tasti speciali di Windows da codice VB.NET . Blocca i tasti CTRL+ESC , ALT+TAB, ALT+F4, uccide il processo TaskMenager quando si fà CTRL + ALT + CANC . Premetto che questo codice è rivelato dagli AntiVirus come probabile Virus e pertanto lo metto a disposizione solo per scopo informativo, quindi non mi assumo nessuna responsabilità sull'uso che ne fate. Dovete creare un file Modulo ed inserire il seguente codice e lo salvate Keyboard.vb : CODICE VISUAL STUDIO 2010 - VISUAL BASIC .NET - VB.NET:
codice:
Imports System.Runtime.InteropServices
Imports System.Reflection
Imports System.Drawing
Imports System.Threading
Module Keyboard
<DllImport("kernel32.dll", CharSet:=CharSet.Auto)> _
Public Function GetModuleHandle(ByVal lpModuleName As String) As IntPtr
End Function
Public Declare Function UnhookWindowsHookEx Lib "user32" _
(ByVal hHook As Integer) As Integer
Public Declare Function SetWindowsHookEx Lib "user32" _
Alias "SetWindowsHookExA" (ByVal idHook As Integer, _
ByVal lpfn As KeyboardHookDelegate, ByVal hmod As IntPtr, _
ByVal dwThreadId As Integer) As Integer
Private Declare Function GetAsyncKeyState Lib "user32" _
(ByVal vKey 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 Structure KBDLLHOOKSTRUCT
Public vkCode As Integer
Public scanCode As Integer
Public flags As Integer
Public time As Integer
Public dwExtraInfo As Integer
End Structure
' Low-Level Keyboard Constants
Private Const HC_ACTION As Integer = 0
Private Const LLKHF_EXTENDED As Integer = &H1
Private Const LLKHF_INJECTED As Integer = &H10
Private Const LLKHF_ALTDOWN As Integer = &H20
Private Const LLKHF_UP As Integer = &H80
' Virtual Keys
Public Const VK_TAB As Integer = &H9
Public Const VK_CONTROL As Integer = &H11
Public Const VK_ESCAPE As Integer = &H1B
Public Const VK_DELETE As Integer = &H2E
Private Const WH_KEYBOARD_LL As Integer = 13
Public KeyboardHandle As Integer
' Implement this function to block as many
' key combinations as you'd like
Public Function IsHooked( _
ByRef Hookstruct As KBDLLHOOKSTRUCT) As Boolean
Debug.WriteLine("Hookstruct.vkCode: " & Hookstruct.vkCode)
Debug.WriteLine(Hookstruct.vkCode = VK_ESCAPE)
Debug.WriteLine(Hookstruct.vkCode = VK_TAB)
'MessageBox.Show(Hookstruct.vkCode.ToString)
If (Hookstruct.vkCode = VK_ESCAPE) And _
CBool(GetAsyncKeyState(VK_CONTROL) _
And &H8000) Then
Call HookedState("Ctrl + Esc blocked")
Return True
End If
If (Hookstruct.vkCode = VK_TAB) And _
CBool(Hookstruct.flags And _
LLKHF_ALTDOWN) Then
Call HookedState("Alt + Tab blockd")
Return True
End If
If (Hookstruct.vkCode = VK_ESCAPE) And _
CBool(Hookstruct.flags And _
LLKHF_ALTDOWN) Then
Call HookedState("Alt + Escape blocked")
Return True
End If
'' disable PrintScreen here
If (Hookstruct.vkCode = 44) Then
Call HookedState("Print blocked")
Return True
End If
Return False
End Function
Private Sub HookedState(ByVal Text As String)
Debug.WriteLine(Text)
End Sub
Public Function KeyboardCallback(ByVal Code As Integer, _
ByVal wParam As Integer, _
ByRef lParam As KBDLLHOOKSTRUCT) As Integer
If (Code = HC_ACTION) Then
Debug.WriteLine("Calling IsHooked")
If (IsHooked(lParam)) Then
Return 1
End If
End If
Return CallNextHookEx(KeyboardHandle, _
Code, wParam, lParam)
End Function
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 Sub HookKeyboard(ByRef f As Form)
callback = New KeyboardHookDelegate(AddressOf KeyboardCallback)
KeyboardHandle = SetWindowsHookEx(WH_KEYBOARD_LL, callback, GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName), 0)
'MessageBox.Show(KeyboardHandle.ToString)
Call CheckHooked()
End Sub
Public Sub CheckHooked()
If (Hooked()) Then
Debug.WriteLine("Keyboard hooked")
Else
Debug.WriteLine("Keyboard hook failed: " & Err.LastDllError)
End If
End Sub
Private Function Hooked() As Boolean
Hooked = KeyboardHandle <> 0
End Function
Public Sub UnhookKeyboard()
If (Hooked()) Then
Call UnhookWindowsHookEx(KeyboardHandle)
End If
End Sub
End Module
Come invocare le funzioni da un From di Windows con due bottoni , copiate il seguente codice.
CODICE VISUAL STUDIO 2010 - VISUAL BASIC .NET - VB.NET:
Imports System.Runtime.InteropServices
Imports System.Reflection
Imports System.Drawing
Imports System.Threading
Public Class Form1
Dim MyThread As Threading.Thread
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Keyboard.HookKeyboard(Me)
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Keyboard.UnhookKeyboard()
End Sub
Public Sub KillProcess(ByRef strProcessToKill As String)
Dim proc() As Process = Process.GetProcesses
For i As Integer = 0 To proc.GetUpperBound(0)
If proc(i).ProcessName = strProcessToKill Then
proc(i).Kill()
End If
Next
End Sub
Private Sub Form1_FormClosed(sender As Object, e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
MyThread.Abort()
End Sub
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
'Questo serve per evitare di far apparire la Task Menager quando si fà Control + Alt + Canc
MyThread = New Threading.Thread(AddressOf UccidiTakManager)
MyThread.Start()
End Sub
Private Sub UccidiTakManager()
Do While True
KillProcess("taskmgr")
Threading.Thread.Sleep(10)
Loop
End Sub
End Class
La mia domanda rimane: non esiste un metodo più semplice per bloccare i tasti CTRL, ALT, F4, TAB e loro combinazioni?
Rispondi quotando
ma scusa, windows prevede di impostare lo screensaver con la richiesta di password alla sblocco...non ti va bene?? Sinceramente non capisco proprio dove vuoi arrivare... come si dice..a pensar male non si sbaglia mai 
