Shell users
From FreeBSDwiki
Shell users: any users logged onto a server interactively via a shell. Includes anyone logged in at the physical console, using ssh, telnet, or any other way you can think of to get a shell. Once you get to the shell, you can freely run any program and/or manipulate any file or directory in any way you choose, subject only to the bounds imposed by your user context.
It is a good idea to minimize the number of shell users on any important server as much as possible.
