FTP communication is not secure, all communication is plain text and can be easily captured. Despite this serious weakness, few do anything to secure it. There are simple ways to correct this with VSFTPD.
SSL/TLS With FTP
Add these settings to your /etc/vsftpd.conf file and you will have an anonymous ftp server that will allow anyone to download files from /home/ftp but they cannot upload. It will also protect all of your users as they must ftp into their home accounts using ssl.