I'm planned to rent a dedicated server at a hosting company. The server will have Debian Lenny 5.0 OS. The purpose of this server is to host my company website, to host email server to manage company emails and to host FTP services.
The Web service is Apache, The FTP is ProFTPd and the mail service is not decided yet but mostly it will be Exim4.
My question is: After server being up and start serving company website visitors and company emails ...etc., what security I should consider to protect my server from any kind of attackers. In particular those attacker who will relay on these 3 services installed on my server?
Thank you in advance