Anti-leech protection in ASP

< %
From_url =   CSTR (Request. servervariables ( " Http_referer " ))
Serv_url =   CSTR (Request. servervariables ( " SERVER_NAME " ))
If   Mid (From_url, 8 , Len (Serv_url )) <> Serv_url Then
Response. Write " Invalid link! "   ' Preventing leeching
Response. End
End   If

If Request. Cookies ( " Logined " ) = ""   Then
Response. Redirect " /Login. asp "   ' Login required!
End   If
Function Getfilename (longname) ' /Folder1/folder2/file. asp => file. asp
  While   Instr (Longname, " / " )
Longname =   Right (Longname, Len (Longname) - 1 )
  Wend
Getfilename = Longname
End Function
Dim Stream
Dim Contents
Dim Filename
Dim Truefilename
Dim Fileext
Const Adtypebinary =   1
Filename = Request. querystring ( " Filename " )
If Filename =   ""   Then
Response. Write " Invalid file name! "
Response. End
End   If
Fileext =   Mid (Filename, Rev (Filename, " . " ) +   1 )
Select   Case   Ucase (Fileext)
Case   " ASP " , " ASA " , " Aspx " , " Asax " , " Mdb"
Response. Write " Illegal operation! "
Response. End
End   Select
Response. Clear
If   Lcase ( Right (Filename, 3 )) = " GIF "   Or   Lcase ( Right (Filename, 3 )) = " JPG "   Or   Lcase ( Right (Filename, 3 )) = " PNG "   Then
Response. contenttype =   " Image /* "   ' No download dialog box appears for image files
Else
Response. contenttype =   " Application/MS-download"
End   If
Response. addheader " Content-Disposition " , " Attachment; filename = "   & Getfilename (request. querystring ( " Filename " ))
Set Stream = Server. Createobject ( " ADODB. Stream " )
Stream. Type = Adtypebinary
Stream. Open
If   Lcase ( Right (Filename, 3 )) = " PDF "   Then   ' Set PDF file directory
Truefilename =   " /The_pai_file_s/ " & Filename
End   If  
If   Lcase ( Right (Filename, 3 )) = " Doc "   Then   ' Set the DOC file directory
Truefilename =   " /My_d_o_c_file/ " & Filename
End   If
If   Lcase ( Right (Filename, 3 )) = " GIF "   Or   Lcase ( Right (Filename, 3 )) = " JPG "   Or   Lcase ( Right (Filename, 3 )) = " PNG "   Then
Truefilename =   " /All_images _/ " & Filename ' Set the image file directory
End   If
Stream. loadfromfile server. mappath (truefilename)
While   Not Stream. Eos
Response. binarywrite stream. Read ( 1024   *   64 )
Wend
Stream. Close
Set Stream =   Nothing
Response. Flush
Response. End
% >