If you want to disallow/deny certain login(s) to your workstation via File Transfer Protocol (FTP), you will need to create a file called /etc/ftpusers because it is not a default file. Add the login name or login names to the file. For security concerns, it is recommended that the root user be added to this file. Below is an illustration of adding login names.
# vi /etc/ftpusers
:wq! (saves and quits vi)