Prevent hotlinking, detect referrer

I'm using a script to force the download of a pdf file.

The script:

<%@LANGUAGE="VBSCRIPT" CODEPAGE="1252"%>
<%
'--------------------------------------------
Response.Buffer = True
Dim strFilePath, strFileSize, strFileName

Const adTypeBinary = 1

strFilePath = "D:\path\pdffile.pdf"
'strFileSize = optional
strFileName = "pdffile.pdf"

Response.Clear

'*******************************
' Requires MDAC 2.5 to be stable
' I recommend MDAC 2.6 or 2.7
'*******************************

Set objStream = Server.CreateObject("ADODB.Stream")
objStream.Open
objStream.Type = adTypeBinary
objStream.LoadFromFile strFilePath

strFileType = lcase(Right(strFileName, 4))

' Feel Free to Add Your Own Content-Types Here
Select Case strFileType
Case ".pdf"
ContentType = "application/pdf"
End Select

Response.AddHeader "Content-Disposition", "attachment; filename=" & strFileName
Response.AddHeader "Content-Length", strFileSize
' In a Perfect World, Your Client would also have UTF-8 as the default
' In Their Browser
Response.Charset = "UTF-8"
Response.ContentType = ContentType

Response.BinaryWrite objStream.Read
Response.Flush

objStream.Close
Set objStream = Nothing

%> 

Code (markup):

Now I want this asp file, let's call it download.asp, to be unable to be hotlinked to, and it shouldn't load if someone just types the url into their browser. What do I add?

Help appreciated, thanks.

 

you could try passing a session variable to download.asp, if lets say
if session("check")="" then
response.redirect "/"
else
your script
end if

ope works for you