You could use ACL whether they be reflexive as previous poster suggested or just extended but the problem you have is that if done properly an nmap port scan is very difficult to block without denying legitimate traffic.
Obviously firewalls will block ports but not the ones you open up and thats the main problem.
IPS/IDS on both the network and the host is the better way to approach this but even they are by no means foolproof.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...