There's no easy way to tell if you didn't already have instrumentation turned on.
The ASA is capable of exporting netflow data to an external collector. It is there that you would be able to retrospectively analyze top flows by source and destination address and port. Additionally in near real time you can monitor the top 10 hosts in the ASDM dashboard (or CLI equivalent).
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...
[toc:faq]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 and UDP are I...