NOTE: If your SFTP session constantly disconnects after several seconds, see this FAQ entry. This document will outline setting up a bookmark in Filezilla to connect to the cluster or other RC file resources you have access to. As such Research Computing is recommending its use over previous clients, especially as it does not have some of the quirks of clients like Cyberduck or SecureFX. It is available cross-platform (Mac, Windows and Linux) and is actively maintained.
Filezilla is a free and open source SFTP client which is built on modern standards.