Distributed denial of service (DDoS)

A Distributed Denial of Service (DDoS) attack is a malicious activity in which a network of compromised computers disrupts services.

Back to glossary

Distributed Denial of Service (DDoS) attacks are a prevalent and potent threat. They can cripple websites, disrupt services, and cause significant financial and reputational damage. This glossary entry will delve into the intricacies of DDoS attacks, providing a comprehensive understanding of what they are, how they work, and how they can be mitigated.

DDoS attacks are not a new phenomenon. They have been around since the dawn of the internet, but their frequency, sophistication, and impact have increased dramatically in recent years. This glossary entry will explore the evolution of DDoS attacks, the different types, and the tools and techniques used by attackers.

Understanding DDoS attacks

A DDoS attack is a malicious attempt to disrupt the normal functioning of a network, service, or website by overwhelming it with a flood of internet traffic. The 'Distributed' in DDoS comes from the fact that the attack source is often multiple, often thousands of, unique IP addresses. This makes it incredibly difficult to stop the attack simply by blocking a single IP address.

DDoS attacks are a type of DoS (Denial of Service) attack, but they are significantly more powerful due to their distributed nature. While a DoS attack may come from a single source, a DDoS attack leverages a network of computers as sources of attack traffic. These computers are often infected with malware and are controlled by the attacker without the owners' knowledge.

The anatomy of a DDoS attack

A DDoS attack typically involves three parties: the victim, the attacker, and the bots or 'zombie computers'. The attacker sends instructions to the network of bots that they control, commanding them to send traffic to the victim's network or website. This flood of traffic overwhelms the victim's network, causing it to slow down or crash.

There are several ways an attacker can create a botnet, or network of bots. They can infect computers with malware, exploit vulnerabilities in software or hardware, or use social engineering techniques to trick users into installing malicious software. Once a computer is part of a botnet, it can be controlled remotely by the attacker, often without the owner's knowledge.

Types of DDoS attacks

There are several types of DDoS attacks, each with its own unique characteristics and methods. The most common types include volume-based attacks, protocol attacks, and application layer attacks. Volume-based attacks aim to consume the bandwidth of the victim's network, protocol attacks exploit vulnerabilities in the victim's server or network infrastructure, and application layer attacks target specific applications on the victim's network.

Each type of DDoS attack requires a different approach to mitigation, making it crucial for organizations to understand the nature of the attack they are facing. For instance, mitigating a volume-based attack may involve increasing the bandwidth of the network, while mitigating an application layer attack may require patching vulnerabilities in the targeted application.

Impact of DDoS attacks

DDoS attacks can have a devastating impact on businesses and organizations. They can cause downtime, disrupt services, and lead to financial losses. In addition, they can damage an organization's reputation, leading to loss of customers and business opportunities. The cost of a DDoS attack can range from thousands to millions of dollars, depending on the severity and duration of the attack.

DDoS attacks can also have indirect impacts. For instance, they can be used as a smokescreen for other malicious activities. While the victim's IT team is focused on dealing with the DDoS attack, the attacker can exploit this distraction to carry out data breaches, malware infections, or other types of cyber attacks.

Case studies of DDoS attacks

There have been numerous high-profile DDoS attacks over the years. One of the most notable was the attack on Dyn, a major DNS provider, in 2016. The attack, which was powered by a botnet of IoT devices, caused widespread internet disruption and affected several major websites including Twitter, Reddit, and Netflix.

Another notable DDoS attack occurred in 2018, when GitHub, a popular web-based hosting service for software development, was hit with a DDoS attack that peaked at 1.35 terabits per second, making it one of the largest DDoS attacks ever recorded. GitHub was able to mitigate the attack within 10 minutes, but the incident highlighted the increasing power and sophistication of DDoS attacks.

Preventing and mitigating DDoS attacks

Preventing and mitigating DDoS attacks is a complex task that requires a multi-layered approach. It involves a combination of technical measures, such as firewalls and intrusion detection systems, and organizational measures, such as incident response plans and employee training.

Technical measures can help detect and block DDoS traffic before it reaches the target network. This can involve rate limiting, IP filtering, and deep packet inspection. However, these measures are not foolproof, as attackers are constantly evolving their techniques to bypass defenses.

DDoS protection services

Given the complexity of DDoS mitigation, many organizations opt to use DDoS protection services. These services provide a range of solutions, from traffic scrubbing to cloud-based DDoS protection. Traffic scrubbing involves filtering out DDoS traffic before it reaches the target network, while cloud-based DDoS protection involves rerouting traffic through a network of servers that can absorb and dissipate the DDoS traffic.

DDoS protection services can provide a high level of protection, but they are not a silver bullet. They should be part of a comprehensive cybersecurity strategy that includes measures to prevent the creation of botnets, such as patch management and malware protection.

Incident response planning

Having an incident response plan in place is crucial for dealing with DDoS attacks. This plan should outline the steps to be taken in the event of an attack, including who should be notified, how the attack should be mitigated, and how the impact of the attack should be assessed. The plan should be regularly reviewed and updated to ensure it remains effective.

Employee training is also an important part of DDoS mitigation. Employees should be educated about the signs of a DDoS attack and the steps they should take if they suspect an attack is occurring. This can help ensure a swift and effective response to an attack.


DDoS attacks are a serious threat in today's digital landscape, capable of causing significant damage to businesses and organizations. Understanding the nature of these attacks, their potential impact, and the strategies for prevention and mitigation is crucial for maintaining cybersecurity.

While it is impossible to completely eliminate the risk of DDoS attacks, a comprehensive approach that includes technical measures, organizational measures, and the use of DDoS protection services can significantly reduce the risk and impact of these attacks.

This post has been updated on 17-11-2023 by Sofie Meyer.

Author Sofie Meyer

About the author

Sofie Meyer is a copywriter and phishing aficionado here at Moxso. She has a master´s degree in Danish and a great interest in cybercrime, which resulted in a master thesis project on phishing.

Similar definitions

Cryptography Arduino Circuit Kali Linux Wireless fidelity Key fob DisplayPort Microsoft Access Obsolete Concatenation Digital subscriber line (DSL) Digital rights management (DRM) Swatting Markov decision process (MDP) Not safe for work (NSFW)