A Denial of Service attack (or short DoS) is an attack by which the server is overwhelmed by requests until it exhausts one of the needed resources (like memory or file handles) and stops responding.

This type of attack does not take special skills; any script kiddie can launch one. However, Lighttpd is not easy to overwhelm, and we can make it even harder.

Before we try to evade them, we need to understand how DoS attacks are carried out. The idea is simple: send as many requests as you can to a server. This means the attacker can maximize the strength of the attacks by distributing the task of sending packets. This is the reason many folks try to take over as many computers as possible by sending out internet worms, creating a "bot-net" of lots of compromised machines.

To make things even worse, the attacker will swamp our Lighttpd with lots of request packets containing bogus IP addresses. So our poor Lighttpd will try to send out responses to other servers...