VSFTPD supports virtual users with PAM (pluggable authentication modules). A virtual user is a user login which does not exist as a real login on the system in /etc/passwd and /etc/shadow file. Virtual users can therefore be more secure than real users, because a compromised account can only use the FTP server but cannot login to system to use other services such as ssh or smtp.
It happens all the time. Sooner or later, every organization may run out of qualified admin staff because of various issues. So how do you deal with fresh out of school admins or other helping people in your organization?
The idea is very simple you want to limit who can use sshd based on a list of users. The text file contains a list of users that may not log in (or allowed to log in) using the SSH server. This is used for improving security. PAM (Pluggable authentication modules) allows you to define [...]