Imagine a popular coffee shop with only one door. On a normal day, customers come and go without any trouble. Now, imagine a hundred people who aren't customers suddenly decide to stand in the doorway, blocking it completely. No one can get in or out. The shop is still there and the coffee is still brewing, but for all practical purposes, it's closed.

This is the basic idea behind a Denial of Service attack. In the digital world, instead of people blocking a door, an attacker sends a flood of internet traffic to a single target, like a website or an online service. When this flood of traffic comes from many different sources at once, it's called a Distributed Denial of Service, or DDoS, attack.

The goal isn't to steal data or break into a system. The goal is disruption. An attacker wants to overwhelm the target's resources—its bandwidth, its processing power, its ability to handle connections—so that legitimate users can't get through. The coffee shop is effectively shut down.

A single person with one computer can't generate enough traffic to take down a major website. That's why attackers build an army. They do this by infecting thousands of computers, smart devices, and servers around the world with malicious software, or malware.

Each infected device, known as a "bot" or "zombie," becomes part of a network called a botnet. The attacker can command this entire network from a central point. When they're ready to strike, they direct every bot in the network to send requests to the target, all at the same time. This creates a massive, coordinated flood of traffic from sources that are difficult to trace and block.

The different ways an attacker can use a botnet to send this traffic are called attack vectors. They might send simple, repetitive requests, or they might exploit specific vulnerabilities in the target's software. Regardless of the method, the principle is the same: use overwhelming numbers to cause a shutdown.

DDoS attacks are not just theoretical. They have been used for decades to cause major disruptions. In February 2000, a series of attacks took down major sites like Yahoo!, CNN, Amazon, and eBay, demonstrating for the first time how vulnerable major online platforms were.

More recently, the 2016 attack on a company called Dyn was one of the largest in history. Dyn provides core internet services, specifically DNS, which acts like the internet's phonebook. By targeting Dyn, the attackers were able to make huge portions of the internet inaccessible, including services like Twitter, Netflix, Reddit, and The New York Times. It showed that attackers could disrupt services for millions of people by hitting a single, critical piece of infrastructure.

While any service connected to the internet can be targeted, some are more common than others. The motivation behind an attack often determines the target.

These attacks are a blunt instrument used to silence, disrupt, or extort. By creating a digital traffic jam with an army of hijacked devices, attackers can effectively take websites and services offline, making them unavailable for everyone.