用Asp隐藏文件路径，实现防盗链

    我们在管理网站文件时，可以把扩展名一样的文件放在同一个目录下，起一个比较特别名字，例如放pdf文件目录为the_pdf_file_s，把下面代码另存为down.asp，他的网上路径为http://www.xx.com/down.asp，我们就可以用http://www.xx.com/down.asp?FileName=51windows.pdf来下载这个文件了，而且下载者无法看到这个文件实际下载路径的！在down.asp中我们还可以设置下载文件是否需要登陆，判断下载的来源页是否为外部网站，从而可以做到防止文件被盗链。 [来源：飞腾设计网www.feitec.com内容，转载请注明出处]

    示例代码： [来源：飞腾设计网www.feitec.com内容，转载请注明出处]

    <%
    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 "非法链接！" '防止盗链
    response.end
    end if
    if Request.Cookies("Logined")="" then
    response.redirect "/login.asp" '需要登陆！
    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 "无效/webpage/asp/041101/24.htm！"
    Response.End
    End if

    FileExt = Mid(FileName, InStrRev(FileName, ".") + 1)
    Select Case UCase(FileExt)
    Case "ASP", "ASA", "ASPX", "ASAX", "MDB"
    Response.Write "非法操作！"
    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/*" '对图像文件不出现下载对话框
    else
    Response.ContentType = "application/ms-download"
    end if

    Response.AddHeader "content-disposition", "attachment; 200497141230.htm=" & GetFileName(Request.QueryString("FileName"))
    Set Stream = server.CreateObject("ADODB.Stream")
    Stream.Type = adTypeBinary
    Stream.Open
    if lcase(right(FileName,3))="pdf" then '设置pdf类型文件目录
    TrueFileName = "/the_pdf_file_s/"&FileName
    end if
    if lcase(right(FileName,3))="doc" then '设置DOC类型文件目录
    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 '设置图像文件目录
    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
    %>