This ColdFusion 8-11 UDF will query the server's request headers to determine if the request is an Ajax form post from jQuery. (jQuery adds a special header to all ajax requests.)

isAjaxRequest.cfm

<!--	Compatible with ColdFusion 8-11.
	4/28/2015 Rewritten to compensate for new undocumented CF10/11 behavior regarding getHTTPRequestData().
	https://bugbase.adobe.com/index.cfm?event=bug&id=3042675
	https://bugbase.adobe.com/index.cfm?event=bug&id=3581691
	http://www.bennadel.com/blog/2824-gethttprequestdata-may-break-your-request-in-coldfusion-but-gethttprequestdata-false-may-not.htm
--->

<cffunction name="isAjaxRequestPost" output="false" returntype="boolean" access="public">
    <cfset var response = StructNew()>
	<cfset response.AjaxHeader = getPageContext().getRequest().getHeader("X-Requested-With") />
    <cfreturn isdefined("response.AjaxHeader") AND response.AjaxHeader IS "XMLHttpRequest" />
</cffunction>

<cfif not isAjaxRequestPost()>
	<!--- log attempt, alert admin, etc --->
	<cfheader statuscode="403" statustext="Forbidden">	
	<cfcontent type="text/html; charset=UTF-8"><cfoutput>Forbidden</cfoutput><cfabort>	
</cfif>

<!--- perform database update, modify cookies, upload files, etc --->
<cfcontent type="application/json; charset=UTF-8"><cfoutput>{"status":1}</cfoutput><cfabort>