ASP.NET Automated Negative CAPTCHA User Control v2

 1 <%@ Control Language="C#" %>
 2 
 3 <script language="C#" runat="server">
 4 
 5     public bool IsValidSubmission()
 6     {
 7         string ncts  = "";
 8         string email = "";
 9         
10         try
11         {
12             ncts  = Request.Form["NCTS"].Split(',')[0];
13             email = Request.Form["Email"].Split(',')[0];
14         }
15         catch { return false; }
16         
17         if (email != null && email != "")
18             return false;
19         
20         if (ncts == null || ncts == "")
21             return false;
22         
23         int timestamp = -1;
24         
25         try   { timestamp = Convert.ToInt32(ncts); }
26         catch { return false; }
27         
28         if (timestamp == DateTime.Now.Hour)
29             return true;
30         
31         if (timestamp == (DateTime.Now.Hour - 1) && 
32             DateTime.Now.Minute < 30)
33             return true;
34         
35         return false;
36     }
37 
38 </script>
39 
40 <input type="hidden" id="NCTS" name="NCTS" 
41        value="<%= DateTime.Now.Hour %>" />
42 
43 <div style="display:none;">
44     Leave this field blank:<br />
45     <input type="text" id="Email" name="Email" value="" />
46 </div>
47 
48 <script language="JavaScript" type="text/javascript">
49     setInterval("document.getElementById('Email').value='';", 250);
50 </script>

1 <%@ Register tagprefix="akxl" 
2              Tagname="NegativeCaptcha" 
3              src="/controls/NegativeCaptcha.ascx" %>

1 <akxl:NegativeCaptcha id="AkxlCaptcha" runat="server" />

1 if (!AkxlCaptcha.IsValidSubmission())
2 {
3     // CAPTCHA is not valid (spam-bot detected)
4 }