... routinely, and fairly easily, circumventing corporate security controls. And that is because traditional firewall technology was not meant to grapple with the diversity of Internet applications of recent
Here is a quick way to drastically improve the security of your OpenSSH server installations. ( I prefer the combination approach with iptables as several comments indicate)
This is a detailed description about how to set up a CentOS 4.4 based server that offers all services needed by ISPs and hosters (web server (SSL-capable), mail server (with SMTP-AUTH and TLS!), DNS server, FTP server, MySQL server, POP3/IMAP, Quota, Fire