FTP Hardening – Secure FTP software by upgrading to latest version
FTP: In WHM >> Service Configuration, there is an option to change 2 settings for FTP.
By default the first will be set to use pure-ftpd (this is good) and the second is to allow anonymous FTP (this is very bad). Unless you really want half the world (the bad half) discovering that you run an open FTP server, turn anonymous OFF.
Each FTP session uses resources, so you should also be careful about how many FTP logons you allow each account in your Feature Lists. Up to 3 is fine - anything over 10 is getting silly and simply invites your users to use your server for file sharing.