you can try one thing, i guess it should work because according to the document:-
Configuring Command Accounting
You can send accounting messages to the TACACS+ accounting server when you enter any command other than show commands at the CLI. If you customize the command privilege level using the privilege command (see the "Assigning Privilege Levels to Commands and Enabling Authorization" section), you can limit which commands the security appliance accounts for by specifying a minimum privilege level. The security appliance does not account for commands that are below the minimum privilege level.
To enable command accounting, enter the following command:
Where level is the minimum privilege level and server-tag is the name of the TACACS+ server group that to which the security appliance should send command accounting messages. The TACACS+ server group configuration must already exist. For information about configuring a AAA server group, see the "Identifying AAA Server Groups and Servers" section on page 13-12.
As far as i know the AAA accounting available on PIX 7.x for Managing System Access is Command Accounting. Please refer following link to configure Command accounting on the device for Administrative access, such as telnet, ssh etc. Here's a sample configuration for PIX 7.2:-
It seems that you are looking to do command accounting for ssh sessions passing through the firewall. If that is the case then accounting information will only include when sessions start and stop, username, the number of bytes that pass through the security appliance for the session, the service used, and the duration of each session.Unfortunately, for such sessions you will not be able to do command accounting.
Please refer to the link given below for more info:
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...