VSFTPD stands for "Very Secure FTP Daemon" is a GPL licensed FTP server for UNIX systems. It is licensed under the GNU General Public License. It supports IPv6 and SSL. vsftpd supports explicit (since 2.0.0) and implicit (since 2.1.0) FTPS. vsftpd is the default FTP server in the Ubuntu, CentOS, Fedora, NimbleX, Slackware and RHEL Linux distributions. It is secure and extremely fast. It is stable. VSFTPD is a mature and trusted solution which 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.
In July 2011, it was discovered that VSFTPD version 2.3.4 downloadable from the master site had been compromised. Users logging into a compromised vsftpd-2.3.4 server may issue a ":)" smiley-face as the username and gain a command shell on port 6200. This was not an issue of a security hole in VSFTPD, instead, someone had uploaded a different version of VSFTPD which contained a backdoor. Since then, the site was moved to Google App Engine.