Also, if you are paranoid you could add an access-list to your VTY line only allowing SSH with an explicit "deny ip any any log" to log any other attempts to connect to the VTY by protocols other than SSH.
The access-class which is applied to the vty ports to limit access is almost always a standard access list which can not check for protocols. It is possible to use an extended access list in an access-class but it is quite tricky and some of the things that it takes to make it work are not intuuitively obvious.
I believe that the transport input ssh is the optimum solution for this.
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...