When you install OpenSSH, you also get SFTP for free: a replacement for FTP. (Note that SFTP is related to FTP by name only.)
SFTP is very useful, but as is normally configured, it does not provide any logging of user’s file transfers. For monitoring usage, this can be a problem.
The original setting in
sshd_config might look like this:
Subsystem sftp /usr/libexec/openssh/sftp-server
This lack of logging is easily remedied; the details can be found in the man page for sftp-server:
Subsystem sftp /usr/libexec/openssh/sftp-server -l INFO
For best results, check your system’s man pages for the available options.