Dim dInfo As New IO.DirectoryInfo("\\156.789.2.169\Test\test")
        Dim oFile As System.IO.FileInfo
        Dim oFiles As System.IO.FileInfo()
 
                        Try
                            If Authenticate("156.789.2.169", "testbenutzer", _
                              "test") Then
                                ' ...
                                For Each oFile In oFiles
                                    IO.Path.ChangeExtension(oFile.FullName, _
                                      ".sav")
                                Next
                                ' ...
                            Else
                                Throw New Exception("Not Authenticated")
                            End If
                        Catch ex As Exception
                            MsgBox(ex.Message)
                        End Try

 Public Shared Function Authenticate(ByVal domain As String, ByVal username _
As String, ByVal password As String) As Boolean
 
 
        Dim pwd As New System.Security.SecureString()
        Dim bAuth As Boolean = False
        Dim entry As DirectoryServices.DirectoryEntry = Nothing
 
        'Durchlaufe das Passwort und hänge es dem SecureString an 
        For Each c As Char In password
            pwd.AppendChar(c)
        Next
 
        'Bewirkt, dass das Passwort nicht mehr verändert werden kann 
        pwd.MakeReadOnly()
 
 
        Dim pPwd As IntPtr = _
          System.Runtime.InteropServices.Marshal.SecureStringToBSTR(pwd)
 
        Try
            entry = New DirectoryServices.DirectoryEntry(String.Concat( _
              "LDAP://", domain), _
              username, System.Runtime.InteropServices.Marshal.PtrToStringBSTR( _
              pPwd))
            Dim nativeObject As Object = entry.NativeObject
            bAuth = True
        Catch ex As Exception
            bAuth = False
        Finally
            entry.Close()
            entry.Dispose()
        End Try
        Return bAuth
    End Function