In computer technology jargon, DoS attack or denial-of-service attack refers to an attempt to make a system or network resources inaccessible to its users. The purpose, target websites and the way the attack is carried out may vary. However, every attack always comprises of attempts to indefinitely or temporarily suspend or interrupt services provided by a host which is connected to the internet.
DOS attack perpetrators usually target those sites and/or services which are hosted on high-profile web servers like credit card payment gateways, banks and even the root nameservers. The technique finds an extensive use in certain games which are used by peeved competitors on games or server owners. DoS attack is also being increasingly used as a form of resistance. In networking technology lingo, DoS refers to a tool for registering dispute. According to Richard Stallman, DoS is a kind of Internet Street Protests. The term is intimately related to computer networking though, not restricted to this field only. A suitable example will clarify the point. DoS is also used in reference to the resource management of CPU.
DDOS also refers to a kind of DoS attack where several compromised systems, which are infected with botnet (botnet is the usual possibility for infection), target a single system causing DoS attack. The DDOS attack victims comprise of targeted end system as well as other systems which are used and controlled by the hackers with malicious intention. Any DDOS attack whether it is inbound if you are victimized to attack or outbound if you are the culprit, directly violates Accepted Use Policy of all recognized and reputed web hosting service providers. The occurrence of every attack will cause suspension of your virtual private hosting via a mull-route for 24-hour.
One common way of attack takes place through saturation of the target machine with external requests for communication. It happens in such a way that the system fails to respond even to the legitimate traffic. Even it responds, it does so slowly that service will almost be unavailable to the intended users. Such attack typically results into overloading of the server. Usually, DoS attacks are executed by either forcing the target systems to reset or taking up its all resources. The system becomes incapable of rendering intended service, thereby creating problems for the users to communicate effectively.
DoS attacks constitute violations of the Internet Proper Use Policy of the Internet Architecture Board. In addition, these attacks also violate the laws of individual countries.