What is a DDoS attack? Types and mitigation strategies

Not every online outage is an accident. Some are carefully orchestrated, meant to disrupt, damage, and draw attention. A DDoS attack is one of the most common methods used for this purpose, and it has become a serious threat to any business with a digital presence.

DDoS attacks are cheap to launch, hard to trace, and increasingly used to target the most sensitive institutions, such as banks, retailers, media outlets, and even hospitals. In a world that runs on constant connectivity, the effects are immediate — websites go down, users get locked out, and trust takes a hit.

In this article, we'll explore what DDoS attacks are, how they work, and why they're so effective. You'll see real-world examples, learn to spot the warning signs, and discover the latest strategies to protect your systems from getting overwhelmed.

What is a DDoS attack?

A distributed denial-of-service (DDoS) attack is a cyberattack that disrupts the normal operation of a target server, service, or network connection. Unlike a traditional DoS attack, a DDoS attack uses multiple compromised devices, making it much harder to defend against.

Dangers caused by DDoS attacks

DDoS causes immediate and sometimes hard-to-recover damage, including:

• Service disruption. The primary goal is to overwhelm a target server or network, rendering it slow, unresponsive, or completely unavailable to legitimate users.
• Bandwidth exhaustion. Many DDoS attacks flood the target with more traffic than it can handle, blocking legitimate requests and consuming all available bandwidth.
• System crashes. The flood of data can cause servers to crash or freeze, leading to significant downtime for businesses relying on those services.

Motivations behind DDoS attacks

The reasons behind DDoS attacks can vary, and attackers often have specific motives for launching them. Whether for political, financial, or competitive reasons, DDoS attacks can have far-reaching consequences.

Most common motivations include the following:

• Hacktivism. Attacks are launched for political or social causes to disrupt organizations seen as unethical or oppressive.
• Extortion. Cybercriminals demand a ransom to stop the attack. Failure to comply results in continued disruption.
• Sabotage. Competitors or adversaries use DDoS attacks to damage an organization's reputation, operations, or customer trust.
• Distraction. A DDoS attack can serve as a smokescreen, distracting from more sophisticated attacks like data breaches or network infiltrations.

How does a DDoS attack work?

A successful DDoS attack works as a well-coordinated and systematic effort to overwhelm a target by sending an enormous amount of traffic to its systems. To understand how these attacks unfold, let's break them down step by step.

1. Preparation and planning

To launch DDoS attacks, attackers often research the target's infrastructure to identify vulnerabilities and weak points. Attackers may also recruit a network of compromised devices (bots) to carry out the attack, which makes it harder to trace the origin of the traffic. Understanding what DDoS does in this phase is key — it identifies weak points and sets the stage for maximum disruption.

2. Building a botnet

The core of many DDoS attacks is the botnet — a network of infected devices, also known as bots. Attackers usually take control of thousands or even millions of devices by exploiting vulnerabilities in internet of things (IoT) devices, computers, and servers. These infected devices are referred to as zombies, and they're often spread across the world, giving the attack a global scale. The devices could be anything from smart home appliances to personal computers.

How does infection happen? The botnet creator often infects devices by spreading malware through phishing emails, malicious websites, or other cyberattack methods. Once infected, these devices become part of the botnet and await instructions.

3. Command and control servers (C&C)

Once the botnet is built, the command and control servers (C&C) take over. These servers are controlled by the attacker and issue the attack commands to the botnet. Essentially, the C&C servers tell the infected devices when and how to attack the target.

The C&C servers often use encrypted channels to communicate with the bots, making the attack more difficult to detect or stop.

4. Initiation of the attack

When everything is set up, the botnet is triggered to flood the target with a large volume of traffic. The traffic could come in various forms — volumetric attacks, protocol attacks, and application layer attacks. This phase highlights the full scope of a DDoS attack in cybersecurity, where multiple vectors are used to degrade or take down a target's operations.

5. Overloading the target

As the traffic increases, the targeted server or network begins to slow down due to resource exhaustion. Legitimate users experience delays, and eventually, the system becomes unresponsive. The attack continues, often forcing the targeted service to go offline.

The most common DDoS tactics include:

• DNS amplification. A common tactic in DDoS attacks, where attackers exploit vulnerabilities in DNS servers to amplify the size of the service attack.
• SYN flood. A type of protocol attack that targets the server's TCP connection handling by sending incomplete connection requests.

6. Execution and impact

At this point, the target is under siege. The attacker's goal is either to disrupt services (causing downtime and service unavailability) or to distract from other malicious activities. Some attackers might demand ransom in exchange for stopping the attack, while others are just trying to make a statement, disrupt operations, or cause financial damage.

The server struggles to handle the constant flow of requests, and downtime ensues, leading to service disruption, potential financial loss, and damage to the company's reputation.

One common question businesses ask is how long does DDoS last, and the answer varies. Some attacks only last a few minutes, while others persist for hours or even days, depending on the resources and determination of the attacker.

Categories of DDoS attacks

DDoS attacks don't all look the same. Some flood the network with meaningless traffic, while others quietly exhaust server resources with seemingly normal requests. To make sense of the chaos, these attacks are generally classified based on which layer of the OSI (Open Systems Interconnection) model they target — from the application itself all the way down to the physical infrastructure.

Here's an overview of the main DDoS attack categories:

Application layer attacks

These attacks focus on Layer 7 — the application layer — where web pages are loaded and API requests are processed. They mimic real user behavior to overwhelm applications while remaining hard to filter out.

• Typical attacks: HTTP floods, Slowloris, DNS query floods.
• Goal: To crash websites or services by exhausting server-side resources.
• Targets: Public-facing apps like shopping carts, login pages, or search functions.

Protocol (infrastructure layer) attacks

Targeting Layers 3 and 4, these attacks exploit the underlying transport and network protocols like TCP, UDP, or ICMP. They aim to exhaust the processing capacity of routers, firewalls, or load balancers.

• Typical attacks: SYN floods, UDP floods, fragmented packet attacks.
• Goal: To disrupt service by breaking the rules of how devices talk to each other.
• Targets: Network infrastructure, gateways, or edge devices.

Volumetric attacks

These are the "blunt force" attacks of the DDoS world — they flood the network with sheer volume, consuming all available bandwidth.

• Typical attacks: DNS amplification, NTP floods, UDP floods.
• Goal: To saturate the internet connection and take the entire service offline.
• Targets: Entire network segments, ISPs, or cloud platforms.

To put it in context, here's how these attacks line up with the OSI model:

DDoS attack examples and real-world cases

Distributed denial-of-service (DDoS) attacks have made headlines over the years for taking down some of the internet's most widely used services.

One of the most well-known examples occurred in 2018, when GitHub was targeted with a record-breaking attack that peaked at 1.35 Tbps. The attackers used a technique called memcached amplification, overwhelming the platform with traffic. Although GitHub responded quickly by rerouting the traffic through a mitigation service, the attack demonstrated just how fast and massive these attacks can become.

In 2016, DNS provider Dyn suffered a major DDoS attack that temporarily knocked major websites offline, including Twitter, Reddit, and Netflix. The attack was powered by the Mirai botnet, a DDoS network of compromised IoT devices like security cameras and routers. This event drew global attention to the vulnerabilities in consumer-grade connected devices.

Amazon Web Services (AWS) reported mitigating a DDoS attack in 2020 that reached 2.3 Tbps, making it the largest on record at the time. While the disruption was contained, the scale of the attack marked a shift toward more powerful and complex threats targeting cloud infrastructure.

These attacks are highly dangerous as they often result in lost revenue, customer trust issues, and high response costs.

How to detect a DDoS attack

Detecting a DDoS attack early is important to minimize its impact. While some disruptions are immediately obvious — like your website going down — others are more subtle and can look like ordinary performance issues, which include:

• Unusually slow network performance. Pages take longer to load or time out entirely, even though user activity or backend operations haven’t changed. _ Unexplained spikes in traffic. A sudden surge in incoming requests, especially from unfamiliar IP addresses, locations, or devices, can signal hostile traffic. These spikes can vary based on the DDoS attack types, such as volumetric, protocol, or application-layer attacks.
• Website or service outages. If your site becomes inaccessible or returns error codes (like 503 Service Unavailable), it might be overwhelmed by fake traffic — a common indicator of a DDoS attack in cloud computing environments where elastic resources are still not infinite.
• Abnormal traffic patterns. For example, a flood of requests hitting a single API endpoint, login page, or checkout flow, often used as a tactic in application-layer attacks.
• System resource exhaustion. Servers run out of CPU, memory, or bandwidth as they try to handle the flood of requests, impacting legitimate users.

To confirm whether you're under attack, review logs and analytics. Also, consult your hosting or content delivery network (CDN) provider.

How to mitigate DDoS attacks

Mitigating a DDoS attack requires a combination of proactive planning, real-time monitoring, and the right defensive tools. Since no two attacks are identical, having a multi-layered enterprise security strategy ensures that you can employ a DDoS protection plan under a wide range of attack types while reducing your threat exposure.

Risk assessment

Consider integrating vulnerability scanning into your routine assessments. Regularly assessing your system's vulnerabilities is crucial to understanding potential weak spots. External vulnerability scanning, in particular, helps identify issues from an outsider's perspective — just like a hacker would.

Traffic differentiation

Distinguishing between legitimate and compromised traffic is the first line of defense. You can use firewalls and intrusion detection systems (IDS) to analyze incoming traffic patterns and drop suspicious requests early.

Continuous monitoring of network traffic

Setting up real-time monitoring of your network helps identify anomalies and attack patterns. Many DDoS mitigation services offer automated alerts to notify your team about traffic spikes and unusual patterns.

Black hole routing

When under attack, redirecting malicious traffic to a null route — a "black hole" — ensures it doesn't affect your servers. While this doesn't prevent the attack, it can isolate it from impacting your website or services.

Rate limiting

Rate limiting restricts the number of requests that can be made from a single IP in a specific timeframe. This measure prevents bots from flooding your system with requests and gives legitimate users a better chance to access your services.

Firewalls and anti-DDoS services

Advanced firewalls can block incoming attack traffic based on signature patterns. Additionally, subscribing to anti-DDoS services helps mitigate large-scale attacks by filtering the attack traffic.

Anycast network diffusion

Anycast routing allows legitimate traffic to be distributed across multiple data centers globally, making it harder for attackers to overwhelm a single point of failure. By spreading traffic out, the attack becomes less concentrated.

Incident response plan

An effective incident response plan ensures your team knows exactly what to do when an attack is detected. The plan should outline procedures for notifying key stakeholders, immediate actions to take, coordination with your hosting or CDN provider for faster response, and communication strategies for informing customers or users about the disruption.

Having a clear plan in place will reduce downtime, minimize confusion, and speed up recovery time.

Increasing DDoS attack threats

The nature of DDoS attacks is changing. While traditional attacks are still a concern, new techniques are appearing that complicate defense efforts and expand the attack surface — the total number of entry points that could be exploited.

The following are some of the emerging trends and the increasing threats in the world of DDoS attacks.

Multi-vector attacks

Attackers are no longer limited to a single type of DDoS attack. Multi-vector attacks combine multiple techniques — such as volumetric, protocol, and application layer attacks — into one devastating strike. These DDoS attacks are harder to block because they target different layers of a system simultaneously, often overwhelming defenses at multiple points in the cyber kill chain.

IoT botnets and Mirai variants

The proliferation of connected devices has led to a rise in IoT botnets — networks of compromised internet of things devices (like cameras, routers, and thermostats). The Mirai botnet, which was responsible for the 2016 Dyn DNS attack, is a prime example. With millions of IoT devices susceptible to compromise, attackers now have an enormous pool of devices to leverage for DDoS attacks.

AI-enhanced automations

Artificial intelligence (AI) is being used to enhance the effectiveness of DDoS attacks. With AI, attackers can automate and fine-tune service attacks in real time, making these attacks harder to detect and mitigate. AI can also be used to adjust the attack's scale and timing based on the system's defenses.

"Carpet-bombing" attacks

In a carpet-bombing attack, the attacker floods a network with traffic across a wide range of IP addresses. This tactic makes it difficult to filter out malicious traffic because it doesn't come from a single source but from many, often making it harder for defenses to identify the attack as malicious.

DDoS as a service

As DDoS attacks become easier to execute, a new DDoS-as-a-service business model has emerged. This model allows attackers to rent botnets or perform service attacks to target their victims. The availability of DDoS tools for hire has lowered the barrier to entry, meaning that even less technical attackers can launch significant disruptions.

With the growing complexity of DDoS strategies, attack surface management has become essential. By continuously identifying, monitoring, and reducing exposed assets and entry points, organizations can make it harder for attackers to find weaknesses, especially in distributed and cloud-native environments.

How organizations can defend against DDoS threats

As DDoS attacks grow more sophisticated, organizations must adopt advanced and proactive strategies to protect their networks and services.

The following are the most common tactics for DDoS protection:

• AI-based detection and mitigation. AI systems can analyze network traffic patterns, learning to identify anomalies or malicious behavior in real time. Such tools allow for quicker responses, reducing the time it takes to detect and neutralize an attack. AI can also be used to automate mitigation, adjusting defenses without human intervention.
• Threat intelligence platforms. By analyzing real-time data from global threat feeds and monitoring sources, organizations can gain insights into ongoing service attack trends and proactively adjust defenses. Threat intelligence helps predict attack patterns, allowing for more targeted defenses.
• Edge computing for enhanced defense. Edge computing allows data processing to occur closer to the source of the traffic, reducing the amount of data that needs to be processed centrally. By distributing traffic load and using edge locations, organizations can divert or mitigate DDoS attacks before they hit the core network.
• Cloud-based DDoS protection services. Cloud providers offer specialized DDoS protection services. These platforms use advanced mitigation techniques, including massive traffic scrubbing capabilities, to filter out malicious traffic at the network edge before it reaches your servers.
• Hybrid defense strategies. Many organizations are adopting hybrid defense models, combining on-premises security systems with cloud-based DDoS protection. Such a multi-layered approach ensures that defenses are robust across all points in the network.
• Real-time monitoring and incident response. By implementing a real-time monitoring solution, organizations can quickly detect traffic anomalies, analyze the scope of the attack, and deploy mitigation tactics. Having a dedicated incident response team ready to handle a DDoS attack helps reduce downtime and ensures that businesses can return to normal operations swiftly.

For organizations looking to strengthen their defenses against DDoS attacks, NordStellar provides an attack surface management service that helps you better understand your company's attack surface, find and fix vulnerabilities in your external digital assets, and meet the necessary compliance requirements.