There isn't any specific fixup being done on sftp as the stream is encrypted.
You will have to open up the appropriate sftp ports on the PIX (if server is on inside) and if server is outside and client inside, should work on the fly as the inside to outside traffic is allowed by default. Is it a general Q or do you have some specific issue ? (Just curious).
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...