Re: how to block Instant Messaging Yahoo, AIM etc..?
Blocking the repsective IM ports will keep the IM's from using those ports. However, IM's like Yahoo, and AOL, will also SEARCH for other ports to use, if their respective default ports have been blocked.
NBAR as previoulsy suggested will take care of those issues. I have supplied the link for you as well.
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...