What is a Denial of Service Attack?


A Denial of Service Attack is one of the most powerful attacks used by black hackers to harm companies or organizations by making their services and resources unresponsive. this type of attack can be launched against the  operating system, the memory, the CPU, or the network bandwidth itself  to deny access to shared resources or services for legitimate users , and that  can be achieved by the following  two forms

  • The first form is to send crafted packets that exploit a vulnerability of the operating system like the ping of death attack which sends a large number of ICMP packets to freeze or crash the system,
  •  Another form,  is to send a large volume of useless traffic, which would occupy all the resources of the server.

The DOS attack  can be easily  amplified by sending a large volume of packets through a large number of sources which will make it more powerful and hard to detect or defend. Furthermore, when the DOS attack launches from different sources, then it is called distributed denial of service (DDOS) which has more power on the victim. The DDOS attack has two stages, the first stage is to search for vulnerable systems on the internet, then install special attack tools on those systems, converting them to bits or zombies that are directly controlled by the attacker. In the second stage, the attacker will send control commands to zombies through a secure channel ordering them to launch a bandwidth attack against the victim and this can be done by using a fake source IP address.



John N. Stewart, senior vice president and chief security  officer at Cisco says: 


DDoS attacks should be a top security concern for
organizations in the public and private sector in 2014