A DDoS attack is a cybercrime where an attacker floods a server, website, or network with a massive amount of malicious internet traffic to overwhelm it and make it unavailable to legitimate users. Think of it like a coordinated traffic jam that clogs a highway, preventing real cars from getting to their destination. The “distributed” part means the attack traffic comes from many different sources, making it difficult to stop.

How a DDoS Attack Works

A DDoS attack is typically carried out using a botnet. A botnet is a network of internet-connected devices, such as computers, phones, and even smart home devices, that have been secretly infected with malware. These infected devices are called “bots” or “zombies.” The attacker, often called a “bot-herder,” gains remote control over this army of devices without the owners’ knowledge.

Once the botnet is ready, the attacker sends a command to all the bots to simultaneously flood a target’s IP address with a torrent of useless data requests. The sheer volume of this fake traffic overwhelms the target’s resources, like its bandwidth and server capacity, causing it to slow down or crash completely.

Types of DDoS Attacks

DDoS attacks can be categorized into three main types based on how they overwhelm the target:

• Volumetric Attacks: These are the most common type and are like a brute-force assault. They flood the target’s network with a massive volume of traffic, such as a UDP Flood or an ICMP Flood, consuming all available bandwidth and preventing legitimate users from getting through.
• Protocol Attacks: These attacks exploit vulnerabilities in a network’s communication protocols, aiming to exhaust server resources. A common example is a SYN Flood attack, which bombards a server with connection requests but never completes the handshake, leaving the server’s connection tables full and unable to process new, legitimate connections.
• Application-Layer Attacks: These are more subtle and sophisticated. They mimic normal user behavior, like refreshing a webpage or performing a search, but at an overwhelming scale. An HTTP Flood attack, for instance, sends a flood of requests to a web server, forcing it to consume resources to respond, eventually causing it to crash.

How to Defend Against a DDoS Attack

Defending against a DDoS attack requires a multi-layered approach:

• Rate Limiting: This is a basic defense that limits the number of requests a server will accept from a single IP address over a certain period, which can help mitigate low-level attacks.
• Web Application Firewalls (WAFs): A WAF filters out malicious traffic before it reaches your web server. It can be configured to block known bad IPs, detect suspicious patterns, and protect against application-layer attacks.
• DDoS Mitigation Services: Companies like Cloudflare and Akamai offer specialized services that use a global network of servers to absorb and filter out attack traffic before it ever reaches your network. This is often the most effective solution for large-scale attacks.