Securing a Linux Server

The importance of understanding how to secure your linux server has never been more important. From the moment your server goes live it will become the target of numerous attacks.  Most are automated script attacks that randomly select an ip and probe it for obvious weaknesses. The consequences of a hacker getting access to your server can be catastrophic. 

Often, a compromised server will not be obvious to the administrator unless he is vigilant at observing the system logs and performance figures. Any server, once compromised in this way can be used for illegal purposes or as part of a 'BOT Net' or for many other activities that consume your resources, can damage your reputation or destroy your business.

Knowing how to maintain a secure server  is the most important part of administering a Linux server connected to the Internet. It is only a matter of time before an insecure server will be attacked and compromised. Just how quickly attacks can start happening was highlighted to me just the other day ...

I was moving several of my sites to a new server which had just been configured. When I happened to take a look at the security log. I could see at that very moment the server was undergoing a brute force dictionary attack against my SSH server.  In this particular case I was saved by one of the most basic rules of security - use strong passwords AND user names. I immediately took steps to harden the server and block any further attacks on the server.