ColdFusion timestamp trick to prevent form spam

I’ve been using the “timestamp trick” to reduce form submission spam for the past few months now. It’s been extremely effective!

Today was the first time I had to employ it on a ColdFusion-based site. The basic principle is the same, but it isn’t readily apparent how to obtain the timestamp.

The following code illustrates it’s use:

Put this on your form page:

<input name="ts" type="hidden" value="#DateDiff("s", CreateDate(1970,1,1), NOW())#">

Put this at the top of your processing page:

<cfset currentTime = DateDiff("s", CreateDate(1970,1,1), NOW())>
   <cfif currentTime - form.ts lt 3>
   <cflocation url="/">
   <cfabort>
</cfif>

That’s it!

Now, any bot that attempts to submit the form in less than 3 seconds will be automatically redirected to your home page, instead of continuing with the processing script.