A Denial of Service (DoS) attack occurs when a computer floods a server or a resource with data requests, overloads its capabilities, and renders it unavailable for other users.
A Distributed Denial of Service (DDoS) attack is an advanced version of a DoS attack. This attack also involves disrupting the normal traffic flow to a server by overloading it with bogus requests. However, as opposed to a DoS attack, a DDoS attack involves sending these requests from multiple computers in multiple locations.
During a typical DDoS attack, a vulnerable computer system is targeted by the attacker. The attacker becomes the DDoS master and, through this computer, further attacks are launched on other systems. The master does this by locating other vulnerable systems and gaining access to them through malware or by bypassing authentication.
Eventually, the number of infected computer systems, or bots, multiply and create a domino effect. This network of bots is called a botnet and is controlled by the attacker (called the botmaster) through a command-and-control server. These spam the target server with numerous requests and make it unavailable to serve genuine users.
Botnets can be incredibly complex and can contain hundreds of thousands of individual bots.
The following are some common DDoS attacks:
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