A Distributed Denial of Service (DDoS) attack is a type of cyberattack where multiple compromised computer systems are used to target a single system, such as a website, server, or network, causing a denial of service for legitimate users. The attackers flood the target with overwhelming amounts of traffic, requests, or malicious data, exceeding its capacity and rendering it unavailable.

Zombie computers, also known as bots, play a crucial role in DDoS attacks. These are computers or devices infected with malware that allows an attacker to remotely control them without the owner’s knowledge. A collection of these bots is called a botnet. The attacker, often referred to as a “bot herder,” uses command-and-control (C&C) servers to issue instructions to the botnet. These instructions typically involve directing the bots to send a flood of traffic to the targeted server.

The compromised zombie computers, acting in unison, bombard the target with traffic from numerous different IP addresses, making it difficult to block the attack by simply blocking one IP address. This overwhelming influx of traffic consumes the target’s bandwidth, processing power, and other resources, leading to service disruption.

The motivations behind DDoS attacks vary. Some attacks are motivated by financial gain, where attackers demand ransom to stop the attack. Others are driven by activism (hacktivism), aiming to disrupt services as a form of protest. Some attacks are carried out for competitive reasons, to sabotage a rival business. Still others are done purely for malicious purposes, to cause damage or disruption.

Defending against DDoS attacks requires a multi-layered approach. Techniques include using firewalls and intrusion detection systems to filter out malicious traffic. Content delivery networks (CDNs) can distribute traffic across multiple servers, mitigating the impact of an attack on a single server. Rate limiting can restrict the number of requests a server accepts from a specific IP address within a given timeframe. Scrubbing centers analyze incoming traffic and filter out malicious requests before they reach the target server. Also, network monitoring and anomaly detection can help identify and respond to DDoS attacks in real-time.