One of the most widely deployed type of attacks is the Denial of Service (DoS) . The purpose of the attack is not to steal or destroy information. It aims in making the target system unavailable to its authorised users. Attacking an Internet server with a DoS attack may result in the Internet Server software to crash. As a consequence, the local network may stay unprotected to further attacks. The attacks are based on some of the pitfalls that the TCP/IP protocol and some of its implementations posses when handling incoming data.

It’s not in the scope of this post to describe all available Denial of service attacks. These are numerous and change depending on the operating system and/or software used.  Some attacks are based solely on flaws discovered on specific applications (i.e. Apache, Windows,bind).  This post describes only the attacks that take place remotely. Cases where the attacker has already an account on the system (or can gain an account) are not few. For these cases attackers usually run applications on the target that forces the server machines to crash by exhausting their resources (file space and/or memory).