I'm currently working on a solution for this… From what I can see, it should be possible.
I'm going through captiveportal.inc right now and figuring out the best way to do it... i'm happy to post whatever code I come up with.
If anyone else has ideas or can provide some insight into how it works currently... I would love to hear from you.
here is a link where we are talking about this problem please join in so the admins know its not just us :-\
http://forum.pfsense.org/index.php/topic,18516.0.html
Linksys RV042
will block a mac if it dose not match the IP that way they would have to know the IP of the MAC they are spoofing this helps alot i dont know if pfsense dose that or not ???
What browser are you using? with our set up, if you hit enter in IE, it just redirects you back to the login page until you click the button, in safari and Firefox, hitting enter will pass you through the portal.
Dyndns is something entierly different.
It is used to update the name of your own dynamic WAN IP.
The problem with paypal is, that they notonly have a single server, but a farmand thus their DNS entry point to multiple IPs.
Thats why names are not supported, since it is currently not implemented to keep track of the changes in their DNS records.