Hi,
What is the filter applied to public interface. If the filter has incoming HTTP in and Incoming HTTP out, then anyone on the internet will be able to view this page. Couple of options:
1. You can remove the rules for HTTP on this filter and this will not allow anyone to view the page and you can enable it whenever you want to.
2. If you have a Firewall or a Router, then you can specify access-lists to block HTTP traffic to public ip address of the VPN3000 and allow only certain (Yourself) ip addresses to go through.
I would recommend that you disable the HTTP rules in the filter applied to the Public port and enable it only when necessary.
Regards,
Arul