Linux Tips 
Block an IP to Speed up Server During DOS Attack(0)
If your Apache server is slow (or if you see tons of “? ..reading..” on Apache Status in WHM) there is a chance that your http server is under a Denial of Service (DOS) attack.
You can check this out by:
Log on your server as root
Type the following command
How to Remove Apache Server Signature
Apache by default puts a “signature” at the end of error pages and directory listings…here is an example of what this looks like:
Apache/2.2.6 (Unix) mod_ssl/2.2.6 OpenSSL/0.9.7a DAV/2 mod_auth_passthrough/2.1 PHP/5.2.5 Server at yoursite.com Port 80
Most people don’t want to display that information to the general public, but luckily, it is easily removed. You can easily [...]
Fix Open Nameservers to Speed up Sites and Prevent DOS
Open nameservers allow anyone in the world to perform queries on them, which can often lead to DOS attacks and slower performance. Most system administrators prefer to have their nameservers restricted and used only by trusted parties. To check your namesevers, use Intodns, a free tool!
To do this kind of setup, you will need [...]
Install APF Firewall For Server Security
A firewall is essential for the security of any server. Below are the steps to setting up APF on your system to control access:
Download and install APF:
cd /usr/src
wget http://www.rfxnetworks.com/downloads/apf-current.tar.gz
tar -xvzf apf-current.tar.gz
cd apf-*
./install.sh