Block an IP to Speed up Server During DOS Attack

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

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