The Spy (on user) tab becomes available in the right configuration panel when Activity is selected in the left tree panel. When active the Activity Menu appears in the menu bar.
The Spy tab is intended for taking a closer look at what a user is doing. It shows FTP commands, replies and file transfers. To spy, select a user from the Users tab, after selecting a user choose the "Spy on User" command from the Activity Menu or simply double-click on the user in the Users tab. This tab allows you to monitor the individual commands sent to the user and the responses, in addition monitor any file transfers in progress.
In case the session using secure-FTP SSL/TLS the number of bits of encryption-strength is shown together with the cipher. If a session was created by re-using an older SSL session this is shown by "r-" in front of the cipher. Secure-FTP clients should re-use SSL sessions for data transfers, since re-using requires much less CPU power for the FTP server.