In computing, a distributed denial-of-service (DDoS) attack is a precarious endeavor to make a machine or network resources inaccessible, thereby causing refutation of service for users of the plagued system. The downpour of inbound messages to the plagued system basically forces it to shut down, thereby refuting service to the system to authentic users.
In a usual DDoS attack, the attacker instigates by exploiting the vulnerable computer system and making it the DDoS master. The attack master, also known as the botmaster, recognizes and vexes other vulnerable systems with malware. Ultimately, the attacker inculcates the controlled machines to launch an attack against a specific target.
Basically, there are two types of DDoS attacks: a network-centric attack (which overkills a service simply by using up bandwidth) and an application-layer attack (which actually overkills a service or database with application calls).
The accretion of packets on to the target system results into a denial of service. Even though the media inclines to focus on the target of a DDoS attack as the victim, but the fact is that there are many victims in a DDoS attack -- the ultimate target and as well the systems controlled by the invader. Even if the owners of designated computers are usually heedless that their computers have been expediently tarnished, yet the chances are that they are likely to undergo a degradation of service and not perform well.