Denial of Service (DoS) attack is an occasion in which a legitimate user or a group of users is prevented from accessing the services and information of network resources they would normally receive. A denial of service attack can also destroy programming and files in a computer system. DoS attack is typically caused by attackers consuming bandwidth and resources by flooding the target with as many packets as possible in a short amount of time. Attackers may also attempt to disrupt connections between two machines, thereby preventing access to a service, or to prevent a particular individual from accessing a service and to disrupt service to a specific system or person. Often, the source IP address of these packets is spoofed, making it difficult to locate the real source of the attack. But a denial of service attack can sometimes happen accidentally due to poor programming or mis-configuration.
Common forms of denial of service attacks are:
- consumption of scarce, limited, or non-renewable resources
- destruction or alteration of configuration information
- physical destruction or alteration of network components
For the distributed denial-of-service (DDoS) attack, multitude of compromised systems attack a single target, which causes denial of service for legitimate users of the targeted system. In the DDoS attack, there might still be a single attacker. Typically, an attacker begins a DDoS attack by exploiting a vulnerability in one computer system and making it the DDoS "master". It is from the master system that the attacker identifies and communicates with other systems that can be compromised (which are often called an DDoS agent, which are remotely controllable by the attacker. With a single command, the attacker instructs the agents to launch one of many flood attacks against a specified target which causes a denial of service of the targeted system or even force it to shut down.
Distributed Denial of Service (DDoS)
Denial of Service (DoS) and Distributed Denial of Service (DDoS)
Related Terms: IP Spoofing, TCP/IP network vulnerability
Reference Links: http://www.cert.org/tech_tips/denial_of_service.html: Denial of Service