Never checked Firewall Builder, need to test this.
On our servers, we have cPanel and install ConfigServerFirewall which is an excellent iptables based firewall which can be fully configured to block/restrict ports you don't want open. CSF includes the Login Failure Daemon (LFD), which will scan log files and monitor failed login attempts, such as login attempts for FTP and E-Mail accounts, and it will block the IP according to the rules you have setup. CSF also offers Connection Limiting, Real Time Block Lists and Port Scan tracking and much more.
CSF is also supported on webmin which is a free alternative to cPanel. Makes it easy to enable/disable or change firewall rules.