Linux Security is a big topic and is difficult to be covered in one post. i will keep posting on this top time to time.

Below is some basic information; how we can secure a linux box.

1. Password Security
2. Directories Permissions/Ownership Security
3. Unnecessary Services
   
4. Network Security

1. Password Security

Make you password strong and lengthy. Combine letters, numbers, and symbols. Use password meter to test your passwords. Do not use root login for your normal work. only use limited users and for installation and other tasks where root login is required you can use su or sudo to become root and perform special task as soon as you are finished with your task press ctrl+D to return to normal user envirement.

2. Directories Permissions/Ownership Security

Linux have very good directory permision system as compared to Windows. All you need is to only change directory permissions where needed. and do not permit access to directoires like /etc /root to limited users as they could read important information that would help them hacking you box. You can use online permission calculator to calculate permisions .

3. Unnecessary Services
You need to disable all services that are not usefull to you. you can use sysv-rc-conf to check and manage all servces and their run levels. To disable a service you can uncheck a service run levels in sysv-rc-conf .

4. Network Security

Network Security is its self a big topic but at basic level you need to check which network services you are running at your linux server ( for example apache/httpd mysql bind ) . You can use firewall to disallow unneccessary access to these services . IPTABLE or IPCHAIN is firewall that is widely used to secure linux server. but for unauthorized access you need to configure each service to disallow. i will try to go in deep details of these services so stay tunned .

Your Comments will be appreciated.