What Is a DDoS Attack? How It Works and How to Stay Protected

A DDoS attack can take a website, online service, gaming platform, or business network offline by overwhelming it with an enormous amount of traffic or connection requests. Unlike many cyberattacks that try to steal information or gain unauthorized access, a DDoS attack is primarily designed to make a service unavailable to legitimate users.

DDoS attacks have become a common threat for organizations of all sizes. Large companies, government services, financial institutions, gaming platforms, and even smaller websites can become targets. Understanding how these attacks work and how organizations defend against them is an important part of modern cybersecurity.

What Is a DDoS Attack?

DDoS stands for Distributed Denial-of-Service.

A DDoS attack occurs when an attacker uses a large number of devices or systems to send excessive traffic or requests toward a target. The goal is to consume the target’s available resources, such as network bandwidth, server processing power, memory, or application capacity.

The word distributed is important. Instead of traffic coming from one computer, a DDoS attack typically involves many different systems at the same time.

When the volume of malicious traffic becomes too large, legitimate users may experience extremely slow performance or may be unable to access the service altogether.

A DDoS attack does not necessarily mean that attackers have broken into the target’s systems. In many cases, the attack simply attempts to overwhelm the service from the outside.

How Does a DDoS Attack Work?

DDoS attacks generally rely on large numbers of devices sending traffic or requests toward a target.

Attackers may control compromised computers, servers, routers, Internet of Things devices, or other connected systems. These compromised devices can form what is commonly called a botnet.

Once a botnet is under an attacker’s control, it can be instructed to communicate with a particular target simultaneously.

The target might receive thousands, millions, or potentially far more requests depending on the scale of the campaign. The systems responsible for handling legitimate users then have to deal with the additional traffic.

If the attack exceeds the capacity of the network or application, performance can deteriorate or the service can become unavailable.

The attacker does not always need to know exactly how the target’s internal infrastructure works. The objective is often simply to generate enough traffic or requests to exhaust a resource.

Why Are DDoS Attacks Called Distributed?

A traditional denial-of-service attack can involve a single source sending a large number of requests to a target.

A DDoS attack, however, distributes the traffic across many different sources.

This makes the attack more difficult to stop because blocking one IP address or one connection does not necessarily solve the problem. Thousands of other systems may continue sending traffic.

The distributed nature of these attacks can also make malicious traffic appear to come from many different locations around the world.

What Is a Botnet?

A botnet is a collection of internet-connected devices that have been compromised and placed under an attacker’s control.

Botnets can contain many types of devices, including computers, servers, routers, cameras, and other IoT equipment.

Devices may become part of a botnet because of unpatched software, weak passwords, exposed services, malware infections, or other security weaknesses.

Once compromised, the device owner may not realize that their equipment is being used as part of a larger attack.

Botnets are not exclusively used for DDoS attacks. Cybercriminals can also use them for spam, malware distribution, credential attacks, and other malicious activities.

Common Types of DDoS Attacks

DDoS attacks can target different parts of a network or application. Some focus on network capacity, while others attempt to exhaust server or application resources.

Volumetric Attacks

Volumetric attacks attempt to consume as much network bandwidth as possible.

The basic idea is straightforward: send such a large amount of traffic toward the target that its connection or network infrastructure becomes overwhelmed.

Large volumetric attacks can create problems not only for the target server but also for surrounding network infrastructure.

Protocol Attacks

Protocol attacks target weaknesses or limitations in network protocols and the systems responsible for handling network connections.

Rather than simply generating the largest possible amount of traffic, these attacks attempt to consume resources such as connection tables or processing capacity.

Network infrastructure, including firewalls and load balancers, can become targets of these attacks because they must process incoming traffic before it reaches the application.

Application-Layer Attacks

Application-layer DDoS attacks target specific applications or services.

These attacks can be particularly difficult to identify because the traffic may resemble legitimate user activity.

For example, an attacker might generate large numbers of requests that cause a database query, search function, or other resource-intensive application process to run repeatedly.

The amount of traffic does not necessarily have to be enormous if each request consumes significant server resources.

What Happens During a DDoS Attack?

The visible symptoms can vary depending on the type and scale of the attack.

A website may become:

• Extremely slow
• Difficult or impossible to access
• Unstable or intermittently unavailable
• Unable to process normal requests
• Unresponsive to legitimate users

Businesses can also experience disruption to internal systems, APIs, online stores, customer portals, or other internet-facing services.

For companies that depend heavily on online operations, even a relatively short outage can result in lost revenue, reduced productivity, and damage to customer trust.

Can a Firewall Stop a DDoS Attack?

A firewall is an important part of network security, but it cannot stop every DDoS attack by itself.

A firewall can identify and block certain unwanted connections and traffic patterns. However, if an attack generates an enormous amount of traffic, the network connection or infrastructure may become overwhelmed before the firewall can effectively deal with it.

This is why DDoS protection generally involves multiple layers.

Organizations may use traffic filtering, rate limiting, load balancing, specialized DDoS mitigation services, content delivery networks, and network providers that can absorb or filter malicious traffic before it reaches the main infrastructure.

Understanding what a firewall is and how it protects your computer and network is useful, but firewall protection should be considered one layer of a broader security strategy.

How Organizations Protect Against DDoS Attacks

There is no single solution that works against every DDoS attack. Effective protection usually combines several technologies and security practices.

Traffic Filtering

Security systems can analyze incoming traffic and identify patterns associated with malicious activity.

Suspicious traffic can then be filtered or redirected before it reaches the application.

Rate Limiting

Rate limiting restricts how many requests a particular source or client can make within a specific period.

This can help prevent individual sources from consuming excessive application resources.

Load Balancing

Load balancers distribute incoming traffic across multiple servers or systems.

This can improve resilience by preventing one server from handling all requests.

However, load balancing alone is not sufficient protection against large-scale DDoS attacks. If the overall traffic volume exceeds the available infrastructure, additional mitigation is necessary.

Content Delivery Networks

A Content Delivery Network (CDN) distributes content and services across multiple locations.

Because traffic can be handled across a distributed infrastructure, CDNs can help absorb and filter certain types of attacks before they reach an origin server.

Many modern CDN providers also offer dedicated DDoS protection.

DDoS Mitigation Services

Specialized DDoS protection providers monitor traffic and identify attacks as they occur.

When malicious traffic is detected, the provider can filter or redirect it while allowing legitimate traffic to continue toward the target.

For organizations that depend on continuous online availability, dedicated mitigation services can be an important part of their security architecture.

Can Individuals Be Targeted by a DDoS Attack?

Yes, although the consequences can be different from those experienced by a large organization.

Gamers, streamers, online creators, and other individuals with publicly accessible internet connections can sometimes become targets.

A successful attack against a home connection may cause severe slowdown or temporarily prevent the person from accessing online services.

Individuals should avoid exposing unnecessary services directly to the internet and should keep routers and connected devices updated. Strong passwords and properly configured network equipment can also reduce the chance that their devices become part of a botnet.

If a home internet connection suddenly becomes unusable during an apparent attack, contacting the internet service provider is often an important first step.

Are DDoS Attacks Used to Steal Data?

A DDoS attack is primarily intended to disrupt availability, not steal data.

However, attackers may combine DDoS activity with other forms of cybercrime.

For example, criminals could use an attack as a distraction while attempting another intrusion, or use the threat of a DDoS attack to pressure an organization into paying money.

This is one reason organizations should not treat a DDoS incident as only a performance problem. Security teams need to determine whether other suspicious activity is occurring at the same time.

How Can Businesses Prepare for a DDoS Attack?

The best time to prepare for a DDoS attack is before one happens.

Organizations should understand which internet-facing services are critical, how much traffic their infrastructure can handle, and who is responsible for responding during an outage.

A good preparation plan can include:

• Identifying critical online services
• Monitoring normal network traffic
• Establishing traffic and performance baselines
• Using appropriate DDoS protection
• Keeping network infrastructure properly configured
• Establishing an incident response plan
• Maintaining communication with internet and security providers
• Regularly reviewing exposed services and infrastructure

Testing the response process is also important. A security team that knows exactly what to do during an attack can often respond much faster than a team trying to develop a plan while the service is already unavailable.

DDoS Attacks Are Becoming More Difficult to Ignore

DDoS attacks are not a new form of cybercrime, but the growing number of internet-connected systems provides attackers with more potential resources.

The expansion of cloud services, IoT devices, online platforms, APIs, and other internet-facing infrastructure has created an increasingly complex environment to defend.

At the same time, attackers continue to look for ways to generate traffic at greater scale and make malicious activity harder to distinguish from legitimate requests.

For organizations, this means availability needs to be treated as part of cybersecurity rather than simply an IT performance issue.

The Bottom Line

A DDoS attack attempts to make an online service unavailable by overwhelming it with traffic or requests. Unlike an attack designed primarily to steal credentials or install malware, the main objective is usually disruption.

DDoS attacks can range from relatively small incidents affecting individual users to enormous campaigns capable of disrupting major online services.

Firewalls, rate limiting, load balancing, CDNs, traffic filtering, and specialized DDoS mitigation services can all play a role in defending against these attacks. The most effective approach is not relying on one security tool, but building multiple layers of protection around critical systems.

As more businesses and services move online, maintaining availability becomes increasingly important. Understanding how DDoS attacks work is therefore not just useful for cybersecurity professionals—it is an important part of understanding how today’s internet is protected.

For a deeper technical explanation of DDoS attacks and mitigation techniques, see Cloudflare’s DDoS attack overview.